Libba Phillips, 40
Charleston, S.C.

When Libba Phillips learned that her troubled younger sister Ashley had gone missing, she wasn't completely surprised. Ashley had been addicted to crack and alcohol since her teens and would often disappear for days. But "the days turned into weeks and the weeks turned into months," recalls Phillips. "And I knew something was wrong."

She never imagined, though, that the months would turn into years—five years. Since Ashley, 23 at the time of her 1998 disappearance, was an adult and had a history of drug abuse, police refused to help look for her. So Phillips took it upon herself, embarking on a cross-country odyssey that took her from her Sacramento home to Tampa's seedy underbelly, questioning prostitutes and coroners for signs of her sister. "I was so fixated on where the hell is my sister," says Phillips. "And I was so angry that no one was giving me the time of day."

As she got a crash course in the world of the lost and the homeless, she realized many other families were struggling too. In 1999 Phillips quit her pharmaceutical sales job and launched the nonprofit Outpost for Hope (www.outpostforhope.org), which has helped at least a dozen families reunite and thousands more look for relatives with mental illness or drug problems. "Each day someone passes a homeless woman on the corner," she says. "They're not considering that that could be someone's lost loved one." Working with two other volunteers on a shoestring budget, she advises families on how to register with missing persons organizations, how to contact the FBI and to work effectively with police. "When I heard what she was doing, I was almost giddy because there was such a need," says Maj. Sam Cochran of the Memphis Police Department.

Gwyn Robson feared for her daughter Marie's life after the 18-year-old went missing from their Maryland home in 2003. But after Phillips advised her on how to attract media attention and to make missing posters, the teen was found after six months. "I wouldn't have gotten her back without Libba," says Robson. "I was at my wits' end."

All the while, Phillips often doubted she would ever see her own sister again. But she continued looking, clinging to precious childhood memories. "We were inseparable," she says. Armed with cigarettes and dollar bills for bribes, she and her stepfather questioned pimps and drug dealers in Tampa, handing out fliers her family had made. One dealer told them Ashley was likely in a crack house. The search consumed her life, taking a toll on her nine-year marriage, which ended last year. "I wasn't a lot of fun to be around," she says.

Then, on Feb. 7, 2003, Phillips' determination paid off. One of Ashley's acquaintances spotted her poster and urged Ashley to call home. She was eight months pregnant and living in a rundown apartment in Charlotte, N.C. Arriving at her sister's side, "I thought I was going to throw up," says Phillips. Ashley was rail thin, in a state of shock with a broken eye socket. "She was childlike," she recalls. "I kept wanting to hug her and she would flinch." Though Ashley didn't remember many details of her time away, Libba learned that her sister had slept on the streets at times and had been badly beaten. "A lot of people harmed her," Libba says.

Ashley soon moved back to Tampa to live with her parents and her baby daughter. But the homecoming was brief. In 2004, Ashley resumed drinking and disappeared one night in pajamas only to be found nine months later. Since then, her life has stabilized. Now 33 and the mother of two daughters, Ashley holds down a full-time job selling cars and takes medication for her bipolar disorder, which was recently diagnosed. (Her family says she is too fragile to comment.) "We don't really discuss the past with her," says her sister Ginny McGee, 24. "But I'm sure she feels grateful to be found." And Libba is thankful to have her Ashley back again. "I had come to believe that my sister was dead," says Phillips, who recently moved to South Carolina to be closer to family. "And through my searching, I've come to a certain level of peace, that all of this has helped thousands of others."

Know a hero? Send suggestions to HEROESAMONGUS@PEOPLEMAG.COM