Lol, there is a clear history of the development of the transistor that pre dates the roswell crash. Working units were developed at the same time as the crash, but the steps in the process well before that are all clearly accounted for. Its exactly what I have been harping on this entire thread - building advanced technologies isn't easy, it takes time to develop the tools needed to develop the end product. The design of a transistor was developed in the 1920s.
This is an absurdly silly conspiracy theory, as one of the key pieces that allowed the advancement to modern semiconductors was moving to silicon, whereas the first ones developed were made using germanium. If we had a working one from alien technology, why didn't we know to use silicon then?