Mysteries of the (Wet) Unknown

My summer research student had a mysterious minor disaster at the end of the day: his backpack (and the textbook inside it) was quite thoroughly damp. The backpack had been fine when he set it down beside his desk early this morning; he only noticed the water damage when he started packing up for home.

We have no idea where the water came from. Apart from the wet spot on the floor where the backpack had been, every surface (and ceiling) in his office seemed completely dry (and no papers or dust showed signs of water). The backpack was damp all over, and the textbook had water damage along all three exposed edges of the pages as if water had flowed over the top and around down to the bottom. There weren't any water bottles that could have leaked, and he was in his office most of the day without noticing a thing.

Because of what we've been studying the past day or two, we both initially concluded that water must have quantum tunneled into his backpack from a nearby pipe. :) My more serious guess is that one of the facilities maintenance people (who've been cleaning the area) came by at a time when we were working elsewhere and spilled a fair bit of water onto (and into) his backpack. My charitable assumption is that they didn't notice the spill at all, or else they surely would have said something or at least made some effort to rescue the book. But even that seems surprising: what are the odds that they'd dump a bunch of water into his backpack and nowhere else?

Whatever the cause, we stayed an hour late at work interleaving paper towels between the pages to draw the water out. If that's helped by morning, we'll proceed to stacking heavy weights on top to flatten the pages. I hope it works! (And if it doesn't, hey, I got a free copy of that book from the publisher last year that I'm not particularly using. Merry Christmas to him, or something.)