Certified auto detailing

My wife had Dave come and pick up her white Mercedes CLK350 for a wash and interior detailing. When she got the car back there was a fairly large irregular shaped area on the right front hood where the Clear Coat looked like it had been eaten away. I immediately called Dave and explained to him what was there and he immediately denied any wrong doing and blamed us for doing it after we got the car back. He didn't even offer to look at the problem to see if it was his fault. I took the car to our body shop and he confirmed that it was indeed a chemical that was used and it ate the clear coat off down to the primer. He had seen this done before with other customers. The cost to repair is going to be approx $500.00 and Dave wont return my calls any more so I can explain the cost, He just keeps texting us to say it wasn't his fault. Going to small claims on this one.