Moreover, if you want to get that prior art on record with the USPTO, one way to do it is to file for a patent then let the application lapse before issuance. It'll then show up on subsequent searches.

We used to do that as a standard procedure. Before a meeting with a client we would write a bogus patent listing everything we could think of about the subject. Then if there was an arguement about an NDA we could prove we were already working on the idea. You can file a PCT application for almost nothing (used to be $20) and never bother taking it to a full patent - cheaper than having a lawyer minute it.

And establishing that is is, in fact, prior-art would require significant legal work which would be expensive.