If in California, all you need is the receipt, and might be the same elsewhere. Cards are not that critical these days, as most people register their camera online and sellers will retain the card if there is a promo running for that product.
I'd try registering online ASAP, which should tell you whether it's legit or greymarket. If greymarket, file a SNAD with ebay. Canon USA will not cover it under warranty.
I tend to shy away from the NY sellers(especially Brooklyn), unless they have a B&M address that checks out for a retail operation.