I'd disagree that it was common knowledge in the 50's...the cover story was pretty effective at the time, given the climate.
I'd also agree with almost everything nightwing said, with this exception...
Your good insite here actually drives to the center of the puzzle. How could such a possible screw up result in the best kept secret in
history ?
I'm not so sure I'd call it the best kept secret...there is plenty of paper trail stating who the principals are, involved with the issue of
national security and the UFO phenomenon (and not just the Roswell incident). Also, the "screw-up" was initially contained pretty damn well, as the
story wasn't even revisited until decades later by Friedmann. Prior to that, nobody in the general public knew anything about Roswell.
A supposed captured UFO would have certainly scared the pants off the Rusians, knowing that the US would reverse engineer the UFO and possibly have
ultra high tech alien weapons availible!
The major flaw in that theory is that, at the time, the story was squashed. To be effective with that objective, it would have been allowed to play
out in the press a bit more...