Took my car in to have front end repaired. When I ...

Took my car in to have front end repaired. When I picked it up my trunk lid had a half moon shaped white spot the size of a tennis ball on it. Spot wasn't there when I took it in and was when I picked it up. They said they don't know what happened to it so they aren't responsible. Have gone there for years. Will never be back again. Very unprofessional in my opinion.