Government or military retrieval policy or set of procedures is absolutely believable.
*shrug*
If a Mig35 crashes on a farm in Pennsylvannia, do you think we should just leave it their for the local yokels to play with?
What strains believability are fantastic descriptions of technology supposedly retrieved, and even more so, jumping to the conclusion that they are of other-wordly origins.
Nothing wrong with a healthy dose of skepticism.