You can answer negative feedback with a little sub note.
Allows you at least to refute clearly vengeful feedback. With something like 'Attempted to use feedback to gain discount' or some such thing
Or if its a result, as you say, of him not sending it back ,then being ruled in your favour, you can contact ebay and they'll likely remove it as it appears to be nothing more than sour grapes. or not, but worth a try.
I have my own method.
"Fantastic buyer,Ultimate Comms,a King among E-bayers ,quick and Reliable"
I ask that you not use it though. A mates GF blabbed in the ebay forum and i got a nasty letter from them
I pleaded ignorance and coincidence.
Unfortunately, ebay is very handy and a huge market. Our own buy/sell is a bit quiet of late and sometimes if it has to go it has to go