Within the U.S. federal government, as there very been anything so secretive that there was never any official documentation on its existence, regardless of classification level?

by LukeBalizet
nobeardpete

This subreddit is quite strict about people's answers including citations to proper documentation to back up their claims. You are asking about things that lack in official documentation. This clearly poses a bit of a problem. Assuming for the sake of argument that the answer to your question was "yes," I'm curious as to what type of sources you expect people could cite in an answer.