Insurance claim problem

#1

I have a used car that was hit in a parking lot. The insurance co of the other driver is denying the claim bc there is some rust on the area and that it looks like it was painted over. I can’t acct for this as there was no dent there before and I have never painted the car. Is is possible that the accident caused exposure of rust underneath paint and that the car was painted over by the dealer or previous owner? I got it from a Nissan dealer (it’s a 99 Nissan Sentra). I did not see the accident, but the person admitted hitting my car. There are a couple other areas that paint has chipped and there seems to be paint (faded, but same color) underneath.