What style of Sub is it? The gen III (4.8/5.3/6.0) vortec engines have issues with piston slap/ knock (which wouldn't start instantaneously), but I've never heard of issues with rod bearing failure, maybe I'm just out of the loop. It could be a OBS sub with a Gen I, though. Either way, 89K is pretty low mileage for such a failure. I'd go the route Thunder suggested. Sometimes just the threat of a lawsuit will take care of things. Don't be afraid to get the BBB involved, etc., if you get any form of proof that the shop was responsible.
I have a friend who is a decent mechanic, and works at Wally world tire and lube. The stories I hear about that place astound me. From minor to stuff I didn't know was possible. The crazy thing is, everyone who works there is going to school (AMI, UTI, MMI, whatever) to be mechanics. You can't teach someone how to be mechanically inclined. I don't trust anyone including the stealer to fix my stuff. I know there are lots of well trained/ educated techs out there, but they never seem to work on any of the vehicles I know of that are taken in for service.
