Think about the odds though. For that to have happened, she'd have had to: i)see something to spark her interest enough to prompt her to go in going a different direction; ii)make a decision not to tell her husband whom she was with, about her change in plan, even though she was experienced in the desert and would've realized she was not appropriately dressed or outfitted for mid-day conditions which she would know would pose an imminent risk to her safety; iii)fallen or somehow become incapacitated without making a noise; iv)become incapacitated in such a remote location that it was not obvious to her husband who was just behind her, where that occurred; v)be so hidden that K9s, drones, planes, searchers, husband, police, random interested people were not able to locate her within the timeframe in which she could possibly have stayed alive; vi)become incapacitated/deceased in such a remote location that her remains have failed to show up in the time since then via a random person just running across them, even though it's been.. almost half a year now.
For people who think on the basis of percentages of likelihoods, all of those things happening simultaneously would be highly unlikely, even though perhaps altogether possible. Nobody can really say if alien abduction could have been a factor either, since alien abductions can't really be proven not to exist, but the chances are infinitesimally small, nonetheless. imo.
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