Is that dark looking stain related to the missing paint? You might check to see if there are any paint recalls. Back in the 80's GM issued recalls for paint related issues on the Grand AM and Corsica models. One was for bad primer that caused the color coat to flake off and the other was for paint that faded quickly.

Both were what they called no notice recalls - which means that because they weren't safety issues, the manufacturer or dealer didn't have to notify customers. They just published the info and customers were on their own to find out. They also had time limits. I had a corsica and found out too late by a couple of months - dealer wouldn't do anything. I don't know if this practice is still happening, but it might be worth it to check.