C.O.D Problem

This might Sound weird to some of you…
I bought a couple green items from someone today and told him to send c.o.d.
Somehow the person accidentally send me money attached in the last badge, so l I took the items out and returned the gold to sender.
I wanted to send the open amount as well but didn’t keep a mail before and after returning so i can’t see the name any more… is there something like a send items box somewhere? So that I can find out to reimburse an outstanding amount?

Cheers!
Schlumpf