If you paid by credit card and it's within 60 days, they can look it up in their system and just refund your card.
It's 30 days for in-store purchases and 45 for online purchases. 60 days for babyGap gift receipt.
If your purchase is past 30 days, the system automatically deletes its record of it and will be unable to retrieve any information about the transaction. You would get a store credit for current selling price of the item.