Unlike traditional credit card companies, Ebay and Paypal advocate on behalf of the buyer. They will work with you to resolve the banjo issue. I would hold off on negative feedback until you have contacted Ebay. Be the reasonable one.
In the future, pay by Paypal. They will freeze the funds until the issue has been settled. The funds go into a Paypal account and they have control over them. They also have the right to freeze your checking account if they suspect fraud. I buy and sell on Ebay and have been on both sides of the issue.
If he is a seller with excellent feedback he is foolish to refuse to discuss a return. Buyers read the feedback.

kat - your buyer sounds like an idiot. Too bad you re-sent the item. Hope it works out for you.
Mary