We had one something like this a little while back.

Thankfully we had not already mailed out the item when the reversal came thru.

The order sat on our waiting payment list so after 4-days we opened a UPI case so we could get our FVF's back.

A couple of days into that 4-days I noticed that the buyer had been made NARU and the UPI case was closed.

So something had gone wrong with the buyer account, we never knew what happened.

But we got our fees back so all good.

Lesson is I guess never mail out until you are 100% certain that payment has been received.