Let's see. End of semester. Study time. Carrel too far from rest room. Wouldn't be surprised if the person arrived at the library prepared for such a contingency. (That's my scenario and I'm stickin' to it. Perhaps my academic library colleagues have similar stories to tell.)
Link to December 14 Boston Globe article, "Damage to books on gays called accidental".
Nearly four dozen books on gay and lesbian studies in a Harvard University library were ruined last month when library staff accidentally knocked over a bottle of urine left behind on a bookshelf, the university said yesterday. The damage to the books, which are housed in Lamont Library, was initially reported as a hate crime by Harvard police because of the subject matter involved, according to a statement released by Evelynn M. Hammonds, dean of Harvard College. But an investigation found that a library worker had spilled the bottle left nearby while reshelving books. At first, the library treated the incident as a prank, according to the statement. The university plans to replace the books soon.