The chain came off my bike today. I got it off the shuttle bus after the trip back to SF, and found the chain had come off and was wedged between the teeth of the pedal gears and the shifter. It's been so long since I've had to deal with that particular little catastrophe that I'd forgotten how to fix it.
After a few minutes of fumbling around I figured out I should upend the bike and stand it on the seat and handlebars, and thread the chain on in reverse. Hands covered in chain grease, but the bike was fine. I should take it in for a safety check soon, make sure nothing is about to fall off.