NEW YORK -- The last time Margie saw her 14-year-old daughter, Kayla, the teen had spent just over a week in a psychiatric hospital and was eager to have a nice meal and do some shopping with her mother.

Margie works as a New York City employee and didn’t want to be identified on camera. But her voice shook with emotion as she shared her story with PIX11.

“She left in the middle of the night,” Margie said of her daughter’s most recent disappearance in August. “Whoever’s harboring her has to be much older, because she’s only 14.”

Margie shared the story of her daughter's spiral from dressing as a 12-year-old angel on Halloween two years ago….to acting out in class and yelling at teachers.

“They diagnosed her with bipolar,” Margie said of the psychiatrists who treated Kayla after a horrifying episode in July.

Margie said she received a call in the middle of the night from a strange guy.

“Come pick up your daughter,” the voice demanded.

“She was dropped off by a McDonald’s by Bartow Avenue and Asch Loop, near Coop City,” Margie recalled.

“She was in a daze, so that’s when I assumed they probably drugged her,” Margie said. “They cut her hair. They dyed her hair. She was wearing short shorts.”

“That’s when I got the impression she was being exploited.”

Kayla Vales, 14, is one of more than 3,000 children between the ages of 10 and 17 who went missing, as of September 30 this year.

Most of them turned up -- 143 didn’t.

Kayla is one who disappeared, turned up, and then vanished again.

“I feel so much for that mother,” said Sister Joan Dawber, Executive Director of Lifeway Network, an organization that provides safe housing for young victims of human trafficking transitioning back to society.

Sister Joan has heard these types of stories before.

“When you think of sex trafficking, it usually begins at age 14,” Sister Joan said, referring to a time in life when girls are most “malleable.”

The girls are vulnerable and often exploited by a guy who presents himself as a “savior.”

“Because he’ been taking care of her, she now has to earn her living,” Sister Joan observed. “Then, the young person is put onto drugs, so they will do what they’re being asked to do.”

Sister Melissa Camardo, the Director of Development for Lifeway Network, said the girls who try to find their way home will often get lured back to the seedy life.

“What we see is very common is the depth of the trauma,” Sister Melissa said. “That core belief that I’m bad or I’m dirty or I’m damaged….sometimes can force people back (into the life).”

PIX11 has been troubled by the disappearance of teen girls for quite some time and profiled the disappearance of 16-year-old Kimberli Amaya last year.

The teen was last seen heading out to Veritas Academy in Flushing, Queens, according to her mother, Magda.

Kimberli had spent her childhood in El Salvador with grandparents, until she rejoined her mother and two younger siblings in Queens. She kept in touch with friends online—and met some new ones.

“I don’t want to give up, no matter what,” her mother Magda told PIX11, choking back tears. “I know she didn’t run away.”

If you have information about a missing girl or boy, you can call Crimestoppers at 1-800-577-TIPS.

You can also learn more about the organization Sister Joan Dawber runs by visiting her group’s website at www.lifewaynetwork.org.