Have you verified that the luggage cover isn't stowed in the center auxiliary box. If you check and it's not there, then I would simply tell the dealer that your car is missing the luggage cover and ask if they could replace it. I would expect a CPO vehicle to have all the parts it came with originally like floor mats, luggage cover, owner's manual, etc. If your car wasn't CPO, then I would say you're on your own. Let us know what you figure out.