MEDFIELD, Mass. (WHDH) — Police say 30-year-old Stephen Ardrey was up to no good, when he met a Medfield teen at the public library then pulled a disappearing act.

Thankfully, the 17-year-old girl and that man were tracked down on the side of the road in Rhode Island.

If it weren't for a heads up driver police and the girl's parents admit it could've ended much worse.

Ardrey appeared in federal court Friday, charged with sex trafficking crimes.

Prosecutors said he picked up 17-year-old Brittany Thompson at the Medfield Library then drove her to Rhode Island.

“I think in a matter of days Brittany would be in a place that we would never get her back,” Michael Thompson, Brittany’s father, said.

Brittany is developmentally delayed and police believe she met Ardrey online days earlier.

“She’s in good health, good spirits, and we’re just happy to have her back

An alert biker spotted the teen walking with the 30-year-old Ardrey alongside a busy highway three days after she was reported missing.

“I slowed down to 5 MPH and stared the guys in the eyes and I knew, I was like 95 percent sure it was them,” the man who spotted Brittany, Jim Pugliese, said.

Federal prosecutors said Ardrey's no stranger to the law; he has at least 5 sex offenses on his record.

Homeland security raided this Rhode Island hotel room, collecting evidence.

Now, victim advocates are helping the teen recover.

“This is just an eye opener that we have predator on the internet targeting our children every day,” Audrey Morrissey of My Life My Voice, said.

The family is still in disbelief, but they are thankful young Brittany is with them, safe.

“We’re so grateful for everyone's help, love and support. Thank you,” Brittany’s brother Eric Thompson said.

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