Who is responsible when ....

[jmorty33]

Took my 2013 F350 in to replace a cracked cylinder head. Had all the symptoms and I knew that's what was wrong. Mechanic agreed. We decided to replace both heads .. new ones, not rebuilds. After completing the repair the shop drove the truck around for two days to make sure all was good. On day 2 during their test drive engine throws a piston rod punching a hole in the block. Who is responsible for the cost of new block and labor to fix it?