the B-2 was certainly open public knowledge by 1996. I visited Whiteman AFB to see a couple of friends who were missile jockeys in about '92 and the B-2s were just being delivered and working up to combat readiness. I can't remember the exact date but surely by the time they were being delivered, they were public knowledge.
Trying to keep something like that secret in Missouri is a whole lot different from keeping it secret in Nevada.
On the subject of the F-117, I thought it was forced into the public eye because one crashed and the public got hold of that fact and pressed the USAF on details. I could be wrong, though. IIRC it was some time between the USAF admitting they existed and coming clean with designation number and photos, hence the whole F-19 conjecture. IIRC, the F-19 stuff was out for quite a while (a year or two?) before the real photos were out.
but the memory isn't what it once wasn't.