What is the rule for a pinsetter stopping a falling pin, and the pin falls after setter goes back up?
Rule 6b of the USBA rules states that a pin that is touched by the pinsetter is not a legal fall. The pin is not legally scored.
However… according to USBA rules that pin must be reset if you have additional balls to throw. That not being an option in most bowling alleys, you could get screwed, I guess.
When I was in a league, we would call the desk to reset the bad pin. It would take a few minutes, which feels like forever, but they always did it.