If the friend is an innocent bystander, so to speak, I could definitely see him going back later after he re-thought his decision to leave. Especially if the driver was a kid BB's age or so. Hindsight is 20/20. Think about it this way...driver friend, if this is all innocent, would have never DREAMED BB wolud vanish from the face of the earth. Sure we read about this stuff, but odds are this person has never known anyone that actually disappeared in his life, so that would not likely be a concern if he was stuck waiting for BB to emerge for a long time. In all reality, I would be a little miffed at first if I was doing someone the favor of a ride/wait and they were taking forever AND wouldn't answer my calls. That is IF I were a 19 year old. I'd probably give up and head home and only after awhile be bothered by it as my imagination ran away with itself. Remember...kids think they and their friends are invincible. Surely nothing would happen to them, it would never cross their minds!
After taking a snooze for awhile, and thinking about it, I might go back just to check if he was hurt or something. If I couldn't find him then I'd figure all was good and go back to bed.
The one thing I do wonder about is; did driver/Old Buddy step forth and contact the parents or LE when he did hear about BB being missing? Or did they have to track him down?
That 'could' be telling, but then again maybe the kid (and I say kid because I've read that this was a high school friend) just got scared when it turned out he was smack dab in the middle of a missing persons case.
Hopefully answers are soon forthcoming.