Taken directly from
http://walmartstores.com/7658.aspx:
Q: Do you accept RETURNS without a receipt?
A: Walmart, for several years, has accepted returns without a receipt, even though many of our competitors require receipts for all returns.
Walmart gives customers the option of a cash refund (if the purchase was under $25), a shopping card for the amount of the purchase (if it was over $25), a credit to the customer's credit card or an even exchange for the product. Also, as applicable, we follow any manufacturer’s warranties.
The card was a "purchase" at the store, and nowhere in the returns policy can I see a restriction or a prohibition on returning gift cards. Whatcha think, Scott?
And there is a 90 day return limit, but that's a moot point.