I had similar with National in MUC recently. Upon return they found a scratch on the rear bumper and noted it. Truthfully we probably did do it as my coworker admitted she had a hard time getting her suitcase in the trunk, and the car was brand new with only 14 km on it. I got a letter a few weeks later noting this, and a missing Engilish CD for the navigation unit, which I told the agent was missing on my return. They will send me a bill when they get an estimate for the repair. Really, do they ever repair small scratches on rentals? I've heard many similar stories from coworkers - avoid National in MUC.