Sigh. I feel for you, MerryRaven. I worked in a campus library in college, and there were more than a few people (often professors, BTW), who seemed to assume that we lowly library staffers were borderline omniscient. My favorite "suggestion" from one of our patrons (probably the snootiest, control-freakiest faculty member in her department) was that, since a lot of the most popular books went on course reserve (2-hour loan) every semester, that we should have at least 2 copies of EVERYTHING, which is of course near-impossible for any library, let alone a campus branch outfit.
By the way, did the guy in your story even bother to look at the due-date slip in his books? Or did he do a remote-renewal thing and fail to note the new return date? Either way, I'm sure he at least wishes that you folks could use telepathy to see exactly which books were overdue in the return stack! Gotta love the library!