More important WHO PAID? You ship to the address supplied by Paypal or Ebay.
If "buyer" who says he did not order then he has left it too late fo a return, and someone must have paid otherwise you would not have dispatched.
It is up to "buyer" to look in his paypal account to see the payment, but you are not obliged to refund now. It is really the buyers problem, why has it taken him so long to take any action.
