If the guy has insurance, you can try and go through it - you will have your choice of company IF they approve the claim. I'd be willing to bet they'll argue the damage was pre-existing, and if he is actually legit enough to be insured, then he's likely to have some sort of disclaimer relating to your cars paint being in good condition.

If he's not insured then you're dependent on good will unless you want to get a solicitor involved.

FWIW - I dropped my old E30 off for a detail a few years back - got a call pretty soon afterwards to say a chunk of paint had lifted off the bumper while they were washing it. I knew it was down to a crap paint-job, so left it at that.