The OP has mentioned a few times in this post that it is a European location. In all my experiences overseas, the return agents look the cars over with a fine tooth comb. I think this may be as there is only one general rental return area, not a vendor specific return. Unfortunately, I don't think a 5 inch scratch will be missed in a European return, especially if it is in Germany.

And, to the gentleman/woman that used a code they were not supposed to and had an accident that they didn't have to pay for...good for you, but if that was my company that paid for the repairs for someone that illegally used my code...I would come after you for damages once I realized the renter was not an employee.