As the title states. I had my clutch replaced at a friend's shop. It's a 2010 Mazda 3 six speed with 150k on it. They gave me a deal, quoted $900 on what was minimum $1200 anywhere else near me, and wound up being an even $1000 after all was said and done. However, they didn't check the transmission mount, and days after the installation the mount has broken, my engine shifted in the bay, and there was some hellacious grinding before I stopped the car and had it towed.

Someone please give me the run down. How customary and/or imperative is it to check the mounts when doing any kind of transmission work like this? Is it on them, or on me? If the motor shifted, what is the likely culprit of the grinding? Was the transmission becoming misaligned? Any advice on what to check, and what's customary to expect as far as ongoing care/"making it right" in these sorts of situations if the mechanic definitely should have checked it out?

Appreciate any insight.