I agree that the authorities would not want to speculate on a crime like this as it would hurt tourism, and inflame a major and powerful company.
My own speculation remains the same. I believe she did hitchhike a ride, and most likely passed over within an hour of getting in the vehicle. I also believe her remains were left somewhere within a mile or so of where she was picked up; not far.
However, there still remains the tiniest chance that she did "run off" and will surface somewhere. Highly, highly unlikely, but wouldn't that be a great outcome! The only reason I hold on to this possibility is that it does seem (based on the little info I have read), that the missing person in question was suffering from unclear thinking.
I agree with the foul play nearby scenario, but also with the impression that Jenny was not thinking clearly. It's remotely possible she's hiding out, although one of her last blog posts said she was hitching to Cancun. Anyone on the Hannah Thomas-Garner thread, like sjm_qc or Dexter, knows that hiding out is certainly possible. Another teen in TX stayed hidden even longer than Hannah's 3ish months. The other "she's alive!" scenario could be trafficking. That's what JR suspected at the beginning. The Corona driver could perhaps be complicit in this. A little extra money....