Minit Man 10 Minit Oil Change

I took my car in for an oil change, and the technician who did the service broke the engine guard plate off of the bottom of the vehicle. They didn't mention the damage and zip-tied the broken pieces back onto the bottom. The only reason I found out was because I was moving across the state, and there was a dragging sound which caused me to investigate.I have pictures to back my claims, but I cannot upload them here. I know it was minutman because the only people to work on my car before the damage was Firestone, and I observed the bottom of the vehicle and witnessed no damage while they were working on it. I contacted the manager and he wanted me to drive back down to corpus Christi to have the damage inspected to see if it was them. How can they tell? Rather than waste 7hours to travel back there for them to tell me it wasn't their fault, so I am warning anyone else who is considering to get work done here to check the service before leaving.