First of all, you can't walk into the usps and do anything....so, call usps and talk to a rep to confirm delivery...second, call ebay...you have to call them early, and most times you will get a call back response.....I have had better luck to call them # 8:01 eastern time.....don't call at 4 pm.... you'll never get thru, and they won't call you back......has the buyer opened a case? If not, there is zero you can do until they do...but speaking with eBay is a good start....also ask usps for advice/what to do the a claim.....and after this is resolved, block the buyer on EBay ....