If you have an egift card, and you type in the card number and the redemption code (aka PIN) at the time of checkout online and then cancel within the 24hr (really until midnight of the following day) period, in my experience, the amount will be "reloaded" onto that egift card number. This makes it very, very important to keep the redemption code (PIN) after using it IF you think there's a possibility of canceling the ticket within the risk-free period. If you delete the email with the code/PIN, you'll need to call Delta and have them cancel the ticket while converting the gift card amount into a voucher that will stay in "My Wallet." Otherwise, the amount will indeed be "reloaded" back onto the card, but you'll have no way to redeem it again without the code/PIN. Delta Customer service cannot get the code/PIN back for you.

At least, that's how it's worked for me, both when I kept the redemption code/PIN and when (ugh) I did not.

Hope that helps.