A while back I wrote about a self-publicising vanity author. One of the details I'd liked to have note was the complete (or near-complete) absence of his books in public library catalogues, but it's almost impossible to actually find a way to cite a "negative search" much less a positive result...
Indeed, that would end up being OR - quite simple OR, but OR all the same. It's annoying when you know something that apparently no-one has published, but there isn't much we can do about it. (Unless you happen to be an expert on the subject and can publish it yourself)