"Nancy Grace" presents a special on cold cases on Thursday at 8 p.m. ET. The special will air again on Friday.
(CNN) -- A surveillance video shows 17-year-old Kara Kopetsky walking out of her high school on May 4, 2007, before classes let out.
She was having a bad day. She'd forgotten one of her textbooks, and that morning she called home and asked her mother to drop it off at the school office. She also asked her mother to wash her uniform so she could work the 4 p.m. shift at Popeye's Chicken.
A bad day got worse when Kara had an argument with one of her teachers in class, according to police and her family. Frustrated, she left campus about 10:30 a.m., ditching school for the rest of the day.
When Kara didn't come home from school as usual, her family -- mother Rhonda, stepfather Jim and stepbrother Thomas -- grew worried. They filed a missing persons report later that afternoon. Police told them they believed Kara was a runaway, and that she'd come back on her own in a few days.
More than three years later, no one can say what happened to the high school junior from Belton, Missouri.
The case remains cold, but her parents are now going public with new details about what was going on in Kara's life before she disappeared.
They say she was being stalked by a former boyfriend and had obtained a restraining order against him two weeks earlier. Police confirm that there was a pending domestic violence case and protective order naming the boyfriend, when Kara vanished. The charged were later dropped.
Investigators say the ex-boyfriend is a person of interest in the case, because he may have information as to her whereabouts and the relationship between the two was tumultuous before she vanished.
The boyfriend, whom we're not naming because he's not been charged, did not return CNN's calls seeking comment. A person who answered the phone at his lawyer's office said there would be no comment.
According to family and police and Kara's MySpace profile, the boyfriend lived in her neighborhood, was 18, and attended the same high school but dropped out earlier the spring Kara disappeared. She described their relationship as on and off.
Police say there has been no activity on Kara's cell phone since shortly after she walked out of school. They followed some pings from the phone, conducted some searches, but found nothing significant. Beyond that, they aren't commenting.
Her stepfather says the cell phone's long silence makes him suspicious.
"This doesn't make any sense," said Jim Beckford. "Kara was on her cell phone sending texts constantly. Her cell phone bill was typically 80-100 pages long."
She left behind most of her belongings -- money, clothes, iPod and a new carton of cigarettes. Her bank debit card was left in her school locker and her bank account, with $150 from her recent paycheck, remains untouched.
Initially, the Beckfords said, police told them to keep quiet about the alleged stalking case. But, because three years have gone by without any solid leads, they are speaking about a startling incident they say one week before Kara vanished.
Kara's parents say the ex-boyfriend showed up at Popeye's on April 28, 2007 and was kicked out of the restaurant by a supervisor. But he came back as Kara got off work at 10:30 p.m., parking his truck around the corner and waiting, according to the Beckfords and court documents.
When Kara left work, they say, he grabbed her and dragged her into his truck. A friend called Kara's cell phone and she answered, saying her former boyfriend had abducted her. Soon afterwards, he pulled off the interstate into a parking lot and Kara jumped out of the moving vehicle to safety. He drove off, leaving her behind.
Kara went to the police station the next day and filed charges and her mother filed for a protective order. In the petition, Kara states why: "Because I am unsure of what he will do next, because the abuse has gotten worse over time."
"We were asked by police to not talk about this" Rhonda Beckford said. "We were also asked by the Belton police to drop the abduction charges against Kara's boyfriend, just a few weeks after she vanished, as a strategy. In case her boyfriend did know where Kara was, he might be more willing to cooperate and help in the investigation if he weren't facing criminal charges."
According to police in Belton, the case is being actively investigated. But with no certain evidence of foul play, police continue to characterize Kara's disappearance as an endangered and missing adult case.
The state of Missouri considers Kara Kopetsky to be an adult because she was 17 when she disappeared.
Belton Police Capt. Don Spears said police are looking at several persons of interest, but haven't narrowed their investigation to focus on a single suspect. And, he said, police still cannot rule out the possibility that Kara simply ran away.
Her family says Kara has no history of running away.
"She is a very beautiful girl and so we often warned her to be careful, but like any teen, she had an attitude that she was invincible," her stepfather said.
An $85,000 reward is offered for tips leading to the whereabouts of Kara Kopetsky or the arrest of anyone responsible for her disappearance.
Police and family urge people to call the Belton Police Department's tip-line at 816-474-TIPS. Kara is described as 5 feet, 5 inches tall and 125 pounds with brown hair and hazel eyes.