How much was this for? Over $250, Paypal *requires* a signature in addition to the tracking. In the paypal dispute, if one is started, once you upload the tracking they will ask for signature confirmation as well. Once you say you did not purchase it, you will automatically lose the dispute and the buyer will get his money back.
To paypal, it does not matter if the item shows as delivered unless it is less than $250. The USPS more than likely did deliver it and this guy is a pro and knows what to look for.
Over $250, Paypal *requires* a signature in addition to the tracking
IF he also used eBay's shipping tool to process it through the USPS, wouldn't "signature req'd" automatically be added ? I would argue that it BETTER be.