Was this a Simple Delivery transaction?  Then,  a  refund is sent to whoever paid for the SD label:

• If you selected 'Buyer pays’ when you created the listing, your buyer will automatically be refunded for any Simple Delivery label that isn’t used after 30 days

• If you selected ‘Seller pays’ and offered free postage on your listing, you'll need to fill out the Request a refund for Simple Delivery form for the label that wasn’t used. Make sure to send your request within 14 days of your item selling.

@susataylo-98