I had the same thing happen to me where I sent off an item and the buyer said he had not received it. I had obtained a proof of postage receipt from the post office and the buyer was aware of this. He asked for a refund but how was I to know he really hadn't received it? so i refused to give a refund. He went through ebay and Paypal who took his side and they refunded him, i was not pleased. They then wanted me to put funds in my Paypal account to cover the cost of the refund which I haven't done as I do not agree with it, so they have since suspended my account so now I just use my partners ebay account to buy or sell, and now I always use recorded delivery.