I once admitted I ripped off one line in a fic from a certain writer, but neglected to say exactly which line. I don't know if I thought it would be obvious or what, even though it wasn't that famous a source. Then someone complimented me on that exact line and I felt terrible. I probably should go back and edit it but it's only on adultfanfiction.net and I like to pretend I never had an account there even though it still exists. The good part is that at least I'm sure nobody is reading it.

But there are probably places where stuff that was lurking in my brain ended up uncredited in my fic, and I still don't remember it to fix it.