No one knows exactly how many there are. Estimates range from 6,000 to as many as 35,000.
Correspondent Vicki Mabrey went to the epicenter of the disaster, Banda Aceh, where three weeks after the tsunami hit, children and parents are still struggling to find each other.
Along the way, 60 Minutes Wednesday also met some of the people who are trying to help.
As the death toll continues to rise, 60 Minutes Wednesday got a firsthand look at what the survivors are up against.
Lt. Commanders Scott Cota and Ramon Cestero, both Navy doctors, are pushing out into the most remote sections of Indonesia's disaster zone. They spend no more than 30 minutes on the ground at each stop, treating injured survivors, and watching for outbreaks of disease.
But it's what they're not seeing in these sections – children -- that surprises them the most.
"Some places none. In some places one or two [children]," says Cota. "Now, as we go more inland, we're seeing larger populations, but we're also finding that of those populations, about 30-50 percent are orphans in some regions."
When you see the water that rushed through the cities and villages along Indonesia's coast, you understand how so many children could be swept away. The wave literally shredded everything in its path, making matchsticks out of houses, crushing cars and beaching boats on streets.
Today, they're still finding hundreds of bodies in the wreckage. The wave tore families apart in an instant, leaving relatives to look for each other -- many with no idea of who may have lived and died.
Those who can are gathering in camps. There are about 100 others in Banda Aceh. Cota says children are at the highest risk for the diseases that follow in the wake of a natural disaster.
"Diarrheal illness, cholera, dysentery, respiratory illness, malaria is endemic in this area," says Cota. "So people with fevers is another thing we'd be looking for, because there's a lot of free-standing water in these villages."
60 Minutes Wednesday stood in one village, wondering how a place once so full of life could suddenly be so empty. One man, Ismael, says he comes here almost every day, still looking for his wife, son and daughter.
Has he given up hope of finding them alive? "I don't know," says Ismael. "I think, not alive."
For the thousands of children who lost one or both parents, natural relationships are being replaced by necessary ones. The 3,000 survivors in one camp came from a nearby island that was decimated -- 150 children have only one parent left, 50 others have none.
Marie de la Soudiere of the International Rescue Committee is trying to reunite families at the camp. She gently questions children like Misri and Mariyati, 12-year-old cousins whose parents are missing and presumed dead.
De la Soudiere will try to locate relatives they can live with. But one little girl is not ready for that.
"She said, 'I only want to live with my parents. I don't want to live with anybody else,'" says de la Soudiere. "It was just so poignant. She won't accept anybody else right now."
De la Soudiere has spent 30 years working with traumatized children, mostly in war zones. What are the psychological implications for children who've been involved in a natural disaster?
"They hurt. They're in incredible distress," says de la Soudiere. "When we talk to the children, at first particularly because they're Asian, but even in other places, they might smile and you think, 'Oh, they're OK.' Within minutes, tears come to their eyes. That's what they're going through right now."
Henry Saputra, 12, says he and his father were praying at their village mosque when the earthquake that triggered the tsunami hit. They were running home to check on his mother and little sister, when he heard the first sounds of panic.
"People started screaming, yelling 'water, water,'" says Henry. "I ran away. I ran away into the rice paddies and I climbed up onto the roof of a house."
But the wave washed him off the roof. "I grabbed onto a coconut tree in the water," says Henry. "Then when it was calmer, I climbed up onto land."
He'd been separated from his family – and was more than a mile from home. "I didn't see anybody. I was all by myself," he says. "I thought it was doomsday. I didn't see anything. All I could see is dead bodies."
When you come to the place where Henry lived, it's easy to see why he thought it was the end of the world. The tsunami bulldozed every house in this once-vibrant fishing and farming village of 6,000 people. Only about 600 of them survived.
Of that 600, just 10 are children. Survivors come to salvage what precious little is left in the rubble, the remains of their houses, and their lives.
Henry has nothing left, not even a picture of his family. He showed 60 Minutes Wednesday the sleeping mat given to him by a friend he now calls his brother. He shares the floor of a classroom every night with 40 other children and adults.
Who will take care of him now? "All the people here," says Henry.
De la Soudiere says finding extended family is the best hope for children like Henry: "I always say that if you start early enough in an emergency, 90 percent of the kids, we will find a relative willing and able to care for that child."
Isn't it a difficult process? "If you believe that, you won't have the determination to find this adult," says de la Soudiere. "I wouldn't look for a needle in a haystack, but I always have looked for relatives for kids. It can be done. It's hard, but a little better than a needle in a haystack."
The place to start searching for lost loved ones at this camp in what's being called the "tracing center."
"The same people will come in days in and days out," says Anton Susanto, who showed 60 Minutes Wednesday lists that UNICEF is compiling with names and locations of survivors. These lists are posted on the wall. "This is especially for the children. We're focusing on the children right here."
They've had only six successful reunifications so far, but Susanto says he expects many more.
"I've been here several days and I thought I'd get over it," says Susanto. "But every time I see a parent, a relative, a grandparent, as they put their hands trying to trace through it and you look into their eyes and their faces, it's indescribable."
The faces staring out may have been swallowed by the tsunami, or they could be just a camp away. At the tracing center, this man showed us pictures of his family. He found one daughter right away when the water receded. He's searching for three more daughters and his wife.
"I know God will make the impossible possible," he says. "Just like what happened with finding my eldest daughter."
Helmina Sitanggang was more fortunate. She came to the tracing center from Jakarta to search for her sister's family. The first day, she found her 13-year-old niece, Deviyani.
"I stayed in the mountains for three days and three nights. After three days, I went back to my village," says Deviyani. "I stayed in an Islamic school. There are no houses anymore there."
Remarkably, they found Deviyani's brother two camps later. However, the children's parents and 5-year-old sister are still missing. A neighbor told their aunt he'd actually seen the rest of them swept away by the rushing water. For now, Helmina says the children are too upset to talk about their parents.
For all the children affected by this disaster, de la Soudiere says returning to a normal routine as quickly as possible is important. School can't start for several weeks in Banda Aceh. So in the camps, aid organizations are setting up classes and games -- anything that lets kids be kids at least for a few hours a day.
"It's proven extremely important, because in the chaos of what has happened, there's no structure, no predictability," says de la Soudiere. "Children are just sitting waiting for God-knows-what. We can recreate a measure of normalcy, normality – a routine. It does mitigate the effects of trauma."
Henry is clinging to the routine he's always known. He still prays five times a day, but they're no longer the prayers of a child.
"When I say my prayers, I feel sad because I remember my family," says Henry. "I ask God to give me a chance to meet my parents in the hereafter."
Produced by Josh Yager and Michael Bronner