Seller trying to scam us on ebay?
So my sister sold her iphone on ebay last month and buyer is responding now that he never received the phone and now he open a case to get a refund(The guy seems like he owns a store or something since he has like 5k stars). Problem is she didn't asked for the tracking option and she mailed it like that. I know she basically screw her self because now the buyer can win any case since there's no proof whatsoever that she sent it except for a receipt. My question is, is the seller trying scam her? I mean the phone could be in his hands, and if is not where is it then! We haven't received it back through mail. What is our options if we have any? Can we send a refund with no phone in our hands? We only have three days to solve this case. Thank you in advance. (No useless answers and no need to reply the obvious just helpful answers)