...If Collin Powell found out that he had been deceived by an incompetent intelligence tip, he probably would have come clean by now.

Possibly not, if revealing the deception would also reveal some sort of critical shortcoming in our intelligence gathering and/or analysis. It might just be safer to sit on it in the hopes that the hole could be plugged before it's exploited again.

I'd bet you're correct, though, that there are wheels within wheels here, some of which we may never know about. There is, after all, apparently a great deal the public does not know about WW2 because the revelations would reflect badly on someone or other. The British govt, for instance, has made it clear that there are some documents that will never be declassified.