my dad has an 04 chevy impala, maroon in color, that he apparently got some flour on a couple weeks ago at his office. he works for a shipping company and i guess he put a damaged bag on top of his trunk to take across the yard because he didn't want to have it all spill in the trunk, anyway some was on the fender/trunk and he didn't get it washed right away. it's been ~ 2 weeks or so and i guess tonight he went to the car wash and after the flour was washed off, the paint was destroyed. here's a pic of what i'm talking about. it kind of looks like in the pic that its bonded to the paint but it's not. if you feel it you can tell the paint is gone and it's down to the metal or primer.

anyone know why this would happen? also, he is getting ready to drop collision and comp off this car in the next month or so but i told him maybe comp would cover that. anyone think so?