Has there ever been an accident where the non moving throttles where a substantial contributing factor, honest question, I don't recall one but there might be those that do ?
What I do know is that moving throttles are by no means an assurance for better piloting per se.
Just look at the TK 737 crash at AMS where there where no less than 3 pilots in the cockpit, the speed decreased too much, throttles iddled but nobody seemed to notice until it was too late anyway.
Also not 100% sure but ASIANA214 also had pilots thinking the AT was still connected, it was not but the non moving throttles seemed to make both pilots non the wiser.