(continued...)
If Bryce were stuck in the dirt, after trying unsuccessfully to pull forward out of the dirt area, he may have simply grown frustrated, and tried rolling in reverse to get out. A person unfamiliar with that area would have NO idea that going in that direction would lead to the small (15- 20 foot) cliff, or that there was a roadway below. He may have even gotten frustrated enough to get out of the vehicle and "send it" rolling backwards... or.... he could have gotten out of the vehicle to try digging, surveying the situation, whatever, and the vehicle simply rolled away unexpectedly.
Again, a very likely scenario that he was NOT inside the vehicle when it crashed.
(As noted before, the area where his vehicle was stuck is soft soil... but the tracks of the vehicle as it rolled backwards take it through the scrubby desert brush, rolling along for about 50 feet before the cliff edge... any tracks in the brushy area would be impossible to discern, and the soft dirt area is, by now, highly contaminated with the footprints of countless investigators)
Finally, relevant or not: I found a new, full, disposable cigarette lighter in the "rubble" of the broken glass/ taillight/ bodywork of the "landing" zone. No idea if Bryce was a cigarette smoker, but, if not, a lighter would indicate possible marijuana (or other "smokeable" drug) use. Yes, there are plenty of reasons to carry a lighter in one's vehicle that do not include smoking of anything... however, it tends to hint towards it.
Bottom line, regarding vehicle details: I think there's a very high probability that Bryce, or anybody, was NOT in the vehicle when it finally crashed. And, even if somebody WAS in it, the chance of a head injury is low, considering that a rear collision would not tend to generate the same impact forces as a side or frontal collision.
