Iwould press them or GM to find out what has happened, like was said above it could have happened at the dealership before you received it. Check to see what date it was shipped to the dealer. I wouldn't trust what the Dealer says.
Sorry to hear this, when I had a 2005 C6 the wife and I stopped at Wally World to pickup some meds and the 10 minuntes we were in the store someone poured a coke on the hood of the car it was on the secuirty cam but we couldn't make out the tag.