Open the door, find a little black foam ring, where is

It'll be a "spare" door panel clip - probably dropped in the factory. I've had a couple of them I've found in a new car over the years - throw it in your glovebox in case you ever need another - which probably won't ever happen:

 

Yeah after that fix, there was a constant odor of gas in our carport: I just threw in the towel and got a new gas cap. Never used their service department again.

The number of fasteners tend to be overkill, so if one is missing a washer, it's likely got no impact. Just hang onto it, in case you ever do pull the panel off.

 

I have found spare screws laying under my seats in new cars that were left there during assembly.