In April of 2016, a parents worst nightmare came true for dad John (who asked that his last name not be used) when his 18-year-old daughter, a senior in high school, went missing. He told the Daily Beast last year that because he had been monitoring and trying to limit his daughter’s interaction with what he deems “the wrong crowd,” he immediately suspected that she was in deep trouble when she went missing.

Months later, after her safe return, John began speaking out about their ordeal to warn other parents.

“If it was up to what I want, I wouldn’t talk about this,” John told the publication. “It’s difficult to go through and emotionally draining. But I feel compelled to help other families and keep them from going through what we did. I’ve got to do something.”

Not content to let the police handle things by themselves, citing their need to “slowly, methodically build an airtight case,” John hired a private firm to help him get his daughter back. “In the time it would’ve taken to build an airtight case, I would’ve lost my daughter,” he said.

But it’s not how he got his daughter back that John wants to talk to parents about. It’s how she got mixed up with sex traffickers in the first place—and John is pointing his finger directly at the popular app SnapChat. In a Facebook post warning parents, he says,

“…never worry about being over protective. In our case, it all started with friends from high school. Beware of Snapchat. It is extremely difficult to monitor effectively and it is used brilliantly by teens trying to escape detection. The only luck we had with Snapchat was to literally grab my daughter’s phone unexpectedly… and look at recent communications, but even that had limited effectiveness.”

John says his daughter was groomed by her captor for over 2 years before her capture, and that a “friend,” a recent high school grad living on her own, was also used to groom his daughter. Advocates say that because each victim is worth literally hundreds of thousands of dollars a year to their pimps, they are willing to put in the time and the work to lure their victims.

Dottie Laster, a San Antonio-based advocate who fights trafficking told the Daily Beast, “Kids are being groomed, lured, and recruited….When kids are worth $150,000 to $300,000 a year on the sex market, [traffickers] are going to spend the time, do the work, show up at football games. They’ll put in the time to do this. If your kids are online, you need to be there,” Laster said.

John says though they knew their daughter had gotten in with a “bad crowd” and they tried to intervene, it was “too little too late”—the groomers had a serious hold on her. “I’m completely transparent. I never tried to portray it to anyone that she was nabbed off the street while carrying her Bible to choir practice,” he said, also adding, “We had no idea it was nearly as bad as it was.”

He goes on to say in his Facebook post:

“We knew some of her friends were trouble and restricted access to them… I went face-to-face with a few of them and assertively demanded they stay away from my daughter. Unfortunately, my actions only reinforced the alienation strategy that was being used against us. We saw problems. We tried many approaches to turn things in a different direction. We never dreamed the trouble we were facing was a dangerous as it turned out to be.”

In hindsight, John seems to wish he had been more vigilant about what social media apps his daughter was on from the GET-GO, rather than waiting to intervene when he realized there was a problem. Now, this determined dad is out to change the laws in his state, advocating that, among other things, Texas increases the age to work in sexually oriented businesses from 18 to 21 and to increases penalties for anyone caught promoting prostitution when the victim is under age 21.

And, he will continue speaking out and warning other parents. “The fight continues, he says. “They messed with the wrong girl.”