The "scratch" you saw, made by the rubber blower, may well be material from the tip of the rubber blower itself (assuming it's not metal), and not a scratch per se. As such it's a deposit on the ridges and not in the groove itself, and should be inaudible as you found. Polyvinylchloride (what LPs are made of) is pretty hard, especially compared to most rubbers and plastics.
It also means it may clean off with some record cleaning fluid and a brush or microfiber terry towel.
It also means it may clean off with some record cleaning fluid and a brush or microfiber terry towel.