You need professional help..(A lawyer)
You ever read a warranty? "You may have other rights which vary from state to state". Well that line applies here as well.
MOST shops have a "We are not liable" sign.. and depending on the laws where the shop is parked... That may, or may not, be true... Some states when you turn a vehicle or other item over to a shop, the shop has responsibility. And is thus liable for any damage that occurs while it is in their custody.
So seek professional help. That is the only advice I can give, since I know not the law where you dropped it off.
Oh, and seek a better shop for your next repair.
Oh, and one other thought: Your insurance company may be willing to make you whole and then they can go after whomever is liable.. But you need to contact them for that.