Thanks for your advice.
So the urologist just called and told me that I have a "benign" papilloma. Since I have been spending the past few days doing extensive reading about bladder growths, I know that this basically means that am 5% of a cancer patient, which is much better than being 100% of one, but still worrying.
Anyway, it's coming out by cystocopic TUR on the weekend. I'm given to understand that this is mostly just like the cystoscopy I just had.
I asked the urologist whether I should be looking forward to years of regular cystoscopies to verify nonrecurrence. He said while it depended on final pathology, probably not. This doesn't quite jive with what I've been reading so far, and I will probably see if I can get one anyway to make sure to my paranoid self that nothing comes back.
The doc says that I should be grateful that my kidney stone brought this incidentally to light and that this saga should all be over on the weekend. It's possible that the papilloma irritated my ureter and contributed to the kidney stone. I have no basis to evaluate the likelihood of this theory---since the kidney stone happened after an extended (and foolish) period of dehydration, which is definitely a condition that causes stones---but if so I may evade another stone as well.