Rich - You have discovered one of the most fascinating features of motorcycle maintenance.
"We had the whole thing back together and then I realized that a spacer ring had rolled under the bedsheet when the wheel came off, and we had no idea where it had come from."
You discovered the "Duplication Syndrome". This means that as you keep working on a motorcycle, and you have a leftover part and it's still all there, that by continuing to work on it, you will eventually duplicate your motorcycle. This is something that some of us more experienced mechanics have discovered.