But if you're a preservation librarian, or a conservator, you get very excited by signs of bug damage. Certainly, if it looks like an active infestation, the collections will be frozen (a standard Integrated Pest Management [IPM] technique) and then cleaned.
But oftentimes the bugs are long gone. They do leave tracks, however, not footprints but rather "chew-prints".
Silverfish are a common pest and do have a tendency to show up in basements or dark, damp corners where people sometimes store their books and papers. Silverfish are a rather primitive insect, with their mouth on the underside of their body. So if you see signs of something scraping away at the surface in little round areas, it is very likely that a silverfish was nibbling at the paper in search of starch.
So I always carry my camera with me, in case I see a truly remarkable book or a truly remarkable example of "previous use"!