So, I looked all over the shop floor, the living room, my car (took it to the scooter shop for the tire change).... nada. I had put it together before I wrote the last note, so I tore it all back down and (lo and behold) it was there in the wheel the whole time. I am just lucky that I didn't lose it! Though it did not seem like it, it was in there with enough tension to survive transport to the shop, a tire change, and transport back without falling out. Whew!
Fortunately with the tub still out, the tear down took about 10 minutes, and put it back together in about 10 minutes.
