The women haven't been seen since that night, when they rented videos in the lobby of the Cedar Lodge.
"A mother, a daughter and an Argentinean citizen have disappeared off the face of the Earth, and that's the big mystery now," Modesto police spokesman Kelly Huston said Monday.
So far, the only solid lead is the discovery Friday of Mrs. Sund's wallet on a city street in Modesto, about 60 miles west of the lodge, on the west fringe of the park in rural El Portal.
Mrs. Sund's husband, Jens, and several members of her prominent Northern California real estate family, the Carringtons, are offering a $250,000 reward for any information leading to their safe return.
They have gathered at a Modesto hotel to help investigators look for clues.
"This is a rental car that's long overdue. We've got a woman who's very meticulous in planning vacations. She has not held to that itinerary or contacted anyone or shown up anywhere," Huston said.
The Mariposa County Sheriff's Department said there is no evidence of foul play, but it hasn't ruled out the possibility of a crime. No suspects have been questioned or arrested.
The FBI is investigating the possibility of kidnapping until the facts suggest otherwise, agency spokesman Nick Rossi said.
Sund said he last saw his wife and 16-year-old daughter, Julie, on Feb. 12, when they left their home in Eureka with Silvina Pelosso, a foreign exchange student from Argentina, to fly to San Francisco.
Mrs. Sund, 43, is a fourth-generation member of the Carrington family, which has been prominent in Sonoma County real estate since 1882. Silvina, 16, is the daughter of Mrs. Sund's former classmate, Raquel Pelosso, who arrived in California on Sunday to join the search.
"At the beginning, we thought it might have been an accident," said Ms. Pelosso, starting to cry. "Something else may have happened. I don't know."
Mrs. Sund rented a car at the San Francisco airport, and drove with the two teen-agers about 60 miles east to Stockton, where Julie competed in a spirit competition as a member of a Humboldt County cheering squad, her father said.
The trio then drove 60 miles south to Merced, where they spent the night. On Sunday, they drove east to El Portal and checked into the lodge.
They went to Yosemite on Monday and returned to the lodge that night. They never checked out the next morning, but visitors to the lodge routinely are awake and gone long before the front desk opens.
The first sign something might be wrong came when Mrs. Sund and the teen-agers failed to arrive Tuesday afternoon at the University of the Pacific in Stockton. The three were supposed to meet a neighbor from Eureka and his mother for a campus tour.
"M wife was trying to get my daughter interested in college. My neighbor showed up with her son, and asked, 'Where is Carole?'" Sund said.
The women also failed to meet Sund at San Francisco airport Tuesday night. They had planned to rendezvous there so Silvina could accompany Sund and the couple's three other children, ages 10, 13 and 14, on a trip to the Grand Canyon.
Sund said he wasn't worried about their no-show at first because his flight from Eureka had been delayed five hours because of a storm, so he left anyway on the flight to Phoenix with his other children.
"It was kind of a confused evening," he said. "I had her paged at the airport. She never responded. I got there about 10:45 (p.m.) with the other three kids. We had 10 minutes to catch our flight to Phoenix."
Sund said he really began to worry the next day, when he still hadn't heard from his wife.
"About 11 a.m. Wednesday, I started making calls and nobody had heard from them. I still thought maybe they were in a motel in San Francisco," he said. "Definitely by 7:30 p.m. Wednesday, I was panicking."
Sund, a vice president at the Carrington Co. real estate investment firm in Eureka, said he last talked to his wife on Presidents Day, when she called him from Cedar Lodge.
"She said they were having a nice trip," he said.
Written By Christine Hanley