I think Target has a policy where you can return two things per year, without a receipt. They require your drivers license, and I think there is a limit in regards to the cost of the item. The limit could be $50, and you of course will get the lowest price it ever sold as.
I think Wal-Mart does this as well.
If you have a Costco membership, and the game was ever sold at Costco's in your city, you can say that you got this as a gift from another Costco member. I'm not sure if Costco would actually look up that members account and see if they indeed did purchase it or not, but normally, Costco has a pretty lenient return policy, for things that were sold in their stores. Costco doesn't carry a big selection of games tho, so very possible they didn't have either of those games for sale.