Thanks for bringing this up. The "blue tarp" has been bugging me. It is definitely an anachronism. Even in my mid 20s, the tarps commonly for sale were still mostly canvas and dark green, grey, or maybe some other earth tone. Plastic ones were just becoming available then, and were usually horribly cheap and unreliable. This would have been just about 40 years after the alleged crash. The seemingly ubiquitous bright blue plastic tarps we see everywhere were not a thing until some years after, like in the 90s.
There were plenty of other anachronisms. This one could be down to Randle or someone else who came along after the original telling. So much of the story is just implausible that I still have trouble wrapping my head around Vallee having anything to do with it.
I suppose those youngsters might have actually seen some weird shit. Weird shit happens in the desert. It looks like if there is anything real in there, though, it has been severely polluted by subsequent events, legends, and wild tales. Randle does a good job of pointing many of them out.
My dad told me about a fighter jet that crashed near the town where he lived when he was a kid. This would have been around 1950, or five years after the story in question here. The military swooped in amazingly quickly, like within an hour, and set up roadblocks all around the farm where the plane came down. Everyone was evacuated immediately and no one was allowed in the area for a couple of days. He said he remembered a couple of farmers fuming and raising hell because they needed to tend their livestock, but the military ignored them. This was for a fairly ordinary airplane crash. Might have been some super secret prototype or something, but it was far from an alien space ship.