as it turns out, heidi allen's i.d.'s filing cabinet somewhere. a deputy actually carried it around with him. and, one day, two years before she disappeared, he lost it, dropped it, in the parking lot of the d&w convenience store where heidi would one day become a cashier. the i.d. was later found. it's essentially like outing an undercover officer or a protected witness. >> yes. yes. the idea that it's out there, that they believe she's an informant is a problem. >> reporter: what was important for lisa peebles about the discovery of the heidi identity card was that even though it was in the brother's case file, it had apparently never been given to gary thibodeau's defense team. she argued that was something prosecutors are required to turn over any evidence that might help the defense. lisa filed a motion to have gary's conviction throw out. and john o'brien broke news, writing the first of many heidi stories to come. >> it just took off, and people are devouring it. >> reporter: a rock had been kicked over. the repo