Somewhere between Wholey's and 12th Street, the nut that held my bicycle seat on fell off.
I know this because I stopped in front of Wholey's to try tightening it, and failed due to lack of tools--specifically, a hex wrench or crescent wrench. At 12th St there was a guy from the construction at the bus depot wearing a belt of tools and I thought he might have what I needed; when I dismounted, however, the seat fell off. It's possible that that's when the nut decided to make its break, but if so I didn't see it.
As far as I know, there's nowhere downtown that sells hardware anymore, and the situation is made even more fun by the fact that my bicycle uses metric screws. Fortunately the maintenance people in my building have a collection of nuts and bolts, one of which was long and thick enough to be pressed into service; it'll get me home, but I don't want to make too many trips on it. It's off to Home Despot or its moral equivalent this evening in search of a 6mm nut (do you measure nuts and bolts from the tips of the threads, or the valleys?).
Because I really needed this today.