Pat,
That's true, but in most (if not all but they don't yet have technology to prove it) cases, it had already escaped the bladder and was just undetectable.
The abstract for this study was in Uro Today Thursday, 21 January 2010 and was published just last month.
Surveillance strategies after definitive therapy of invasive bladder cancer
It certainly doesn't mean you need no follow up but the probability of recurrence is extremely reduced.
It also is indicative that a higher number of lymph nodes being removed is better and that if they are all negative for cancer the probability of recurrence is even lower.
They have some good charts in the study as well as some good information. It is pretty long but it's not a difficult read.
Mike