Hey there! Nice to meet you!
Based on your description, it appears that the owner of the payment card used to purchase your Fortnite in-game items disputed the transaction with the bank as unauthorized, and the bank agreed to issue a refund.
According to the official Microsoft website: https://support.microsoft.com/account-billing/what-is-a-chargeback-890da6ef-971a-4811-ad95-5dc5d29a4f95
"Chargebacks, or transaction reversals, happen when you inform your bank, credit card company or other financial institution, such as PayPal, that you dispute a payment made by them on your behalf, on the grounds that it took place without your consent. Sometimes your financial institution may contact you to report a suspicious transaction and, if you agree, initiate a dispute on your behalf.
If you encounter a specific issue with a game or app purchased through the Microsoft Store or have reason to request a refund, you should contact Microsoft Support. Repeated misuse abuse of chargebacks can be considered fraud. https://support.microsoft.com/account-billing/help-with-microsoft-store-purchases-4f615f2a-6bbd-fd69-6695-ae213d63eef0 "
Thank you for your kindness and understanding! Please feel free to let me know if you need anything else.
Best regards,
Darhyl