false damage claim

I recently returned a rental vehicle to Enterprise Rental and when I got there they told me the car had a dent, and took me out to show me an area inside the front of the rear wheel well cover that had an indented area that looked like something smooth had punched it in.  My husband drove the car to and from work for a week, parking in his spot, and other than that it was parked in our driveway.  

The damage they showed me could not have been consistent with being parked in a parking lot or a driveway, and my husband didn't hit anything with it.  The damage had no sharp edges, and no paint either chipped or transferred.  I told them it couldn't have happened while we had it.

When I picked up the rental I did not look at that area of the car, but just checked briefly for any obvious dings, and took no photos (my bad).

I think they are scamming customers.

The person behind me in line returning their vehicle was having the same issue.  They were being told of damage that happened that they knew nothing about...

We have never had a problem with a rental car agency before, but were usually in smaller cities than Houston, TX, where we rented this one. We are very disappointed because we have been good customers for Enterprise in the past.