It APPEARS SOMEWHAT that your mind MAY be open fractionally enough to be influenced by quality evidence. I'd be keenly interested if you read the entire 570 pages of Greer's newly published book DISCLOSURE
whether you'd come away with your feelings/opinions now entirely intact. That would be very interesting.
I've not read, "Disclosure," and would be interested in it's salient points. Having said that, here's another plausible explanation...Supersonic research was at it's height around that time-frame; Yeager broke the SB in October '47. Isn't it possible that the gov't lost 1 or 2 test pilots in the run-up? Is it possible the gov't pledged anonymity to the families of said test pilots, esp. in that erea, if they came from Ex-Nazi, Japanese, Sovier or E. European families?
At that point in history, the world's most experienced rocket and jet pilots were nazi's and japanese. The U.S. and Brits had some minor experience in the XP-59 and Gloster Meteor, but nothing to compare with the Komet, the Me-262 or some of the rocket propelled Kamikaze bombs. Just one other, equally well documented, speculative theory. Aliens, possibly...just not of the extraterrestrial sort.
There is the distinct possibility that a balloon figured in the accidental downing of a 509th flight with atomic weapons on board, or the downing of a very secret test aircraft, like the predecessor to our space vehicles. A vehicle named the 'dinasoara' (I think that's correct) was being developed for if and when we achieved space flight -it was an experimental lifting body design. The definitive argument for the flight being extra-terrestrial in origin is yet to be made.