A little background on me.
When I was 14-17 I had a good friend. His parents were "good friends" too.. His parents provided the pot and booze on a NIGHTLY basis and KNEW I wasn't aloud to be at their house, yet allowed me to do so anyways. My parents had made it VERY VERY clear that they didn't want me there my first visit at 14. From that point on I didn't text or call my friend or his parents. They didn't go on my Myspace or Facebook. If something had happened to me while I was there, it is VERY unlikely there would have been identifiable communications with these people and it would seem as if I had left school and then disappeared.
Honestly, I wish LE would release some more info (i.e. urine on clothes) to let us know how likely it is that she just left with someone her parents were unaware of, or thought she had stopped talking to months or years earlier. Based on the unconfirmed rumors, it seems unlikely, I did want to share that some young people keep some of their friends off "the radar" because they want to hang out with people they know they shouldn't.