While rummaging through my computer bag today, I found that one of the USB keys was missing from the pocket in which it ordinarily lives. I went through the bag and could find it nowhere else. I think it may have fallen out of the bag while I was in Illinois, probably in my hotel room. I've left a message with the hotel's lost-and-found (only open weekdays), and mentioned the loss of the headpiece from my CPAP mask as well. I doubt I'll get either of them back, but it's worth trying.
Fortunately, there was nothing irreplaceable on the key, and it wasn't even a very large one at that.