Going off of the list that Crystal posted above, I ruled out most of them either due to age or timeframe. (Disappointing, the last one on the list had already been ruled out as Michael; pretty sure I posted about that above.) One DID stand out, though, especially considering how close to the disappearance it was:
1968 Skeletal remains were found on June 6 at Hermit Rapids in Grand Canyon. These are believed to be the remains of David Jensen, but no positive identification made. Manner of death was
undetermined.
Hermit Rapids is about an hour and a half north on routes 64 and 180; if the police's assumptions were wrong about this being David Jensen, maybe it's worth mentioning that this might be Michael?
I'm at work right now, and when I mentioned this case to my coworker, she added that, because of the time it took Michael's family to report him missing, they might have been involved. My gut says they weren't, that they just weren't that close (especially since, during that time, it might not have been uncommon to quit school and find work while still a teen, so he could have just been independent), but I wanted your thoughts on the matter.