Recently on startup I started getting an OpenSSH dialog warning me of an unknown host key. I then allowed it to store the key, and now I get a a password window at startup.
So then I went and cleared every known cache I could find, including recentf, .ido.last, and everything in my .emacs.d/savefile directory and it keeps bringing up of that OpenSSH password pop-up. What's even weirder is that the host it originally complained about not knowing the key for doesn't exist in my .ssh/known_hosts file, nor is there a system wide /etc/ssh/known_hosts file.
I can solve the problem of the pop-up from coming up every time by following the instructions here but I'm still quite miffed that I can't find the source of what file tramp is trying stat. It seems as if there is some other file I don't know about that's 1) caching some file on that host, and 2) some other unusual place that's caching the host's key.
Some other details: I'm running a prelude based emacs installation. Recently updated from Ubuntu 15.10 to 16.04 and wondering if that has anything to do with it.