Yes, I have had something similar to this happen with a brand new Landcruiser. The dealer didn't put the cap on and the oil leaked out and caused a lot of problems. We had to replace the engine block and the dealer had to pay for it.
This was a million years ago, but I still think you should get a lawyer or go to court.
If it's relevant to small claims court, get your paperwork in order and you can represent yourself. This will depend upon the amount of damage ($) involved. You will need something written out by other people, such as a mechanic who saw the damage. good luck