I had the same thing happen to me not so long ago. I ordered an item on eBay for the full Buy It Now price and paid straightaway, only to find when I got back from work the following day that the seller had refunded my money without my consent! I contacted him to ask for an explanation and he told me that the item I'd ordered was out of stock, although the listing had said that there were six available. I replied that he should have told me first and offered me the option to choose a second choice option instead (there was more than one variation of the item listed), but as a result of his actions I hadn't even been given that option. Had he done so I may have chosen to proceed with the sale regardless, albeit choosing a different variation available on the listing.
As a result of the seller's actions I went to leave the appropriate negative feedback, only to find that I couldn't do so because the seller had issued me with a full refund, despite the fact that the seller had refunded the money without discussing the matter with me, and without my consent. Anyway, I forgot about it until about two or three weeks later when I was looking at my purchase history and saw that eBay had put a reminder on the page saying something along the lines of "Leave feedback for the following items", although the message had not been there previously. I clicked on the reminder and amongst some items that I'd not long placed orders for and was still waiting to receive I spotted the item that eBay had prevented me from leaving feedback for. I decided to try leaving the appropriate negative feedback for the item for a second time and this time the comment stuck.
In light of the above, should you find yourself in a situation whereby you cannot leave the appropriate negative feedback for the seller as a result of the seller having failed to honour the sale and instead refunding the money without your consent wait for a few weeks - three at the most - then look at your purchase history page to see whether there are any eBay reminders to leave feedback. If, as in my case, eBay end up reminding you to leave feedback for the item for which you received a refund that you did not agree to, you ought to be able to leave the seller the appropriate negative feedback, which will also hit him/her with another well-deserved defect.
