I think it's been mentioned before, but stealth does not an invisisble plane make. The key to actually using it effectively is using it in a combined force op with SEAD/DEAD aircraft flying as shotgun cover for it. Also something that is needed is not being predictable or consistant with your approach routes. As was mentioned, if you fly the same routes, same speed, same altitude night after night, eventually you'll get caught.
Also, from what I heard from a F-117 pilot turned F-15 pilot, the F-117 in question was bagged by the very NVA tactic of spamming the skies with active radar and semi-active radar missiles, one just got lucky enough to bag the -117.
And think about this, the military in all chances did request permission to take out the crash site and any location holding the debris. Because it was a war waged from 20,000 feet, and it had to be ass-kissed all the way because the politicians kept a hammer lock on targets, the politicians likely didnt want to appear to be "dirty" and destroy the remains and kill anyone stupid enough to dance around it.