buyer going through paypal for refund saying he didn't buy the item. This was back on July 5

[jonbonfreak]

paypal  contacted us last week indicating that a buyer had informed them that he did not purchase the item.  I did everything through ebay, including postage.  This was back in the beginning of July.

What should I do?  I don't want paypal returning money for an item he did buy.  My understanding is that buyers are to go through ebay for this as well instead of paypal.