It can take up to ten business days for a refund to appear on your bank statement.

If we refunded your order soon after you placed it, make sure the original charge still appears on your statement. Quick refunds can cause the original charge to be reversed instead of refunded: "In the case of a reversal your customer won't see a refund credit on their statement—they'll just see the original authorization drop off their statement entirely after a few days. There will be no payment and no refund. It'll appear as if the whole transaction never happened. Their bank should be able to confirm this for them."

If you paid using a PayPal account, the refund may have gone to your PayPal balance instead of your credit card.