paypal tracking is real usps tracking number, should work

If the tracking shows delivered, then paypal will give money to seller, if tracking shows no information, then paypal will give money to buyer because they didn't get the item. If your package was lost by USPS, then you won't get your money back unless you buy insurance. I have lost several package by USPS and USPS never pays me, but just filed claims to look for it, never heard from them. So it's basically seller's lost when USPS lost your package and you should buy USPS insurance if the item is expensive.