Produced by Chuck Stevenson and Lucy Scott
[This story was first broadcast on May 7, 2011. It was updated on June 5, 2012.]
(CBS) DALLAS -- On a chilly night in Dallas, friends Tina Wiley, Tammye Markle and Joni Shannon are out trying to solve a mystery. They are looking for clues at the home of their old friend, Lisa Stone, who vanished without a trace last spring.
"For her to go missing for even one day is highly unusual and abnormal," Tammye tells "48 Hours Mystery" correspondent Maureen Maher. "We had to take matters into our own hands at that point... Somebody had to look for Lisa."
Lisa, 51, was last seen alive near her home in a Dallas suburb on June 5, 2010.
The search has taken her friends down memory lane... all the way to back to high school, where in the late 1970s, Lisa was a sexy, high-kicking cowgirl with the Mesquite High drill team.
The old friends had first gotten back together at a school reunion in 2009, where they reminisced about old times.
"We went out a lot on weekends to the disco - snuck in sometimes. We were a little underage," Tina recalls with a laugh. "She loved that... She loved to have a good time, and she loved to dance."
The women caught up and talked about how all of their lives had gone in very different directions.
Joni Shannon was a home maker with a Harley and Tammye Markle had spent a lot of her life coaching beauty pageant contestants.
Tina Wiley spent years managing a construction business. Away from work, she had become obsessed with Facebook.
"She thought I was "The Facebook Queen," she says of Lisa. "She thought I was the expert."
Lisa Stone had been in newspaper ad sales until she lost her job in 2006. She, too, was a huge Facebook fan.
"I think that Facebook made her feel very young. I think she could relive her youth," says Tina.
After the reunion, they used Facebook to keep in touch.
Asked about Lisa's personality on Facebook - whether she was private or "let it all hang out" - her friends say, "You knew everything, every detail of her life."
One detail everyone knew was that Lisa Stone loved to be loved.
"She always had a very strong desire to be loved," says Tammye.
"She was very insecure actually...she was always looking for acceptance," says Tina.
"I think that need to be loved caused her to overlook a lot of things," adds Tammye.
Lisa grew up in a wonderful family. Her father was a Dallas cop; her mother, a homemaker, took care of Lisa, her two brothers and an older sister.
But Lisa's cheerful spirit had taken a beating over the years, battered by tragedy after tragedy. Her sister had been killed in a car crash, her beloved brother, Dennis, died of AIDS and her mother died of cancer. In 2005, her father, with whom she had been living and caring for, passed away.
"There were a lot of people that were very concerned for Lisa," Tina tells Maher. "It just seemed things were just spiraling down for her..."
The loss of her brother Dennis, who was gay, cut especially close.
"Growing up in Mesquite in the 70s - it was very conservative. You didn't discuss such things," says Tina.
It wasn't until that high school reunion that Lisa finally discussed her own secret.
"At the party she passed around this little souvenir she had from Six Flags and it had a picture of her partner," Tina says. "That's kind of how she told people there."
"She was expecting, I think, when she passed around that picture, people would go 'your partner? You mean you're gay?' And everyone went 'that's nice,'" says Tammye.
The woman in the picture was Sherry Henry.
"...Lisa is my partner of 15 plus years," she tells Maher. "When I first met Lisa, I walked into the club and she was across the way. And our eyes met (laughs)... She came over and started chatting with me and we hit it off."
Sherry says they became a couple "almost immediately."
"Were you in love with her?" Maher asks.
"Very much," says Sherry.
"And she was in love with you?"
"I would hope," she replies with a laugh.
After Lisa's dad died in 2005, Sherry came around more and more, eventually moving in in 2009.
Asked if she considered herself married, Sherry says, 'Yes."
As a couple, she says hey shared a lot. "We grew up both in the Midwest - strong family values," says Sherry.
And apparently, Lisa happily shared a $300,000 inheritance with Sherry.
Friends say the couple lived off the inheritance until early 2010, when Lisa suddenly realized she was broke.
"One day she came to me and just said she was out of money," Sherry tells Maher.
"Was that surprising to you?"
In early June 2010, the relationship between Sherry and Lisa came to an end - an abrupt end - when, according to her friends, Lisa vanished.
"I noticed I hadn't talked with her in about two weeks," says Tina.
There were no postings on Facebook and no photos. There was nothing for days from the woman who never skipped a single day on the social media site.
"So I immediately got on the phone and started calling Sherry," Tina says. "She kept giving me different stories right away: 'Lisa's off doing odd jobs.' And like late at night. So immediately I started contacting Joni and Tammye."
"When you told me 'Lisa is missing. She hasn't been heard from in a few weeks,' I immediately knew--my heart started pounding," Tammye says to Tina.
"And that's when all of us just got involved trying to piece this thing together," says Tina.
Sherry says there's nothing to piece together.
Asked if she filed a missing persons report, Sherry says, "No, I did not."
"Was there ever a time when you thought, that as her life partner, that you should file a missing persons report?" Maher asks.
"No I did not," Sherry replies. "At the time, prior to me leaving Dallas, Lisa Stone is not missing."