New details on relationship between former teacher and missing student

Newly-uncovered deleted email drafts between Tad Cummins, 50, and Elizabeth Thomas, 15, showed a romantic relationship between the two, according to investigators.
4:32 | 03/27/17

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Transcript for New details on relationship between former teacher and missing student
we'll turn to new detays about that missing Tennessee teacher and the 15-year-old student. He's accused of kidnapping her and authorities revealing the secret way they may have communicated before disappearing two weeks ago and ABC's Eva pilgrim is in Tennessee with much more. Good morning, Eva. Reporter: Good morning, David. This morning marks two weeks since the two disappeared. Police have gotten over a thousand tips, but not a single credible sighting. Investigators say they have no clue where the two could be. This morning, Elizabeth Thomas' family hoping this newly released video of the 15-year-old seen here with her brother -- You want to start from the back or do you want to start from the front? Reporter: Will help the public recognize her voice. She speaks with a very slight lisp just very slight. You'll recognize her voice if you hear it. Reporter: Authorities now revealing new details on how Elizabeth and her former teacher 50-year-old tad Cummins were communicating just days before he allegedly kidnapped her. Investigators uncovering deleted e-mail drafts between the teen and her teacher left through a computer at their school. They were save the message and let it save as a draft. The other person would log in, ride the message and then delete it. Reporter: The messages investigators say showed a romantic relationship. I saw you standing next to your backpack this morning and makes a reference to a body part of hers and, you know, talking about how nice that looked. Reporter: Authorities also saying Cummins researched covert ways to communicate through Instagram and specific encrypted texting apps but Elizabeth's sister telling ABC news Cummins didn't just send messages saying her sister complained he showed up to her workplace as recent as the Saturday before the pair disappeared. She would go and tell people to they will them -- him that she wasn't there and she would go and hide until he left and she thought it was really weird. Reporter: Despite a national alert police say there haven't been any credible sightings of the two since Elizabeth was dropped off by a friend at a restaurant two weeks ago. It feels like she just vanished. And I know that's impossible like someone had to see her. Reporter: Her large family in constant contact with each other waiting holding on to each other and holding on to hope. We just live for that day when we're going to get a phone call that says I'm all right. I need somebody to come get me. Reporter: Authorities think the two are staying out of the public eye. They're asking people to keep an eye out of places like campgrounds, parking lots and in rural areas. Eva pilgrim in Tennessee, Eva, thank you. I want to bring in former FBI special agent Brad Garrett. Always great to have you with us. We heard what Eva reported that so far two weeks and no credible sightings. What does that tell you. It tells me two things if they are still alive and hopefully they are, he has found a place to secrete them basically off the grid, in other words, a remote cabening by a lake, maybe he has a campsite. I'm going to guess he prestaged that. Maybe with food, other items, so that they could go there and hide because that's literally the only way they're going to survive at least in the short run. Brad, we know that a lawyer for the 15-year-old's family now says that there was a time when she was at work and would tell co-workers to lie when he would show up, that she wasn't there but when in fact she was actually hiding so there have been problems along the way. And there clearly is in every one of these relationships where you have a 15-year-old and an older adult. I mean, the realization will set in with the 15-year-old like what am I doing? And then the adult becomes more dominating and domineering and I think that's probably what you see in that particular example. I'll tell you there was one thing in Eva's report that will make any parent's heart race when they hear of this draft e-mail way to communicate. Start a draft e-mail that nobody sees and nobody sends and communicate that way. Al Qaeda has used it. Paula Broadwell used it. Type in an e-mail, save it as a draft and someone that has access to the same account logs in, pulls up the draft, reads it, neither answers it, deletes it but it never goes out in the system so law enforcement or anyone else couldn't capture it. Brad Garrett with us, we always appreciate your insight. Let's all hope that 15-year-old is okay. Yes, indeed.

This transcript has been automatically generated and may not be 100% accurate.

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