That's a common problem with USPS. They can get lax and not scan items on delivery.
Since you paid for s.c., you can take your payment/paypal receipt to the post office and get a refund for the $1.95 you paid for s.c. since they didn't perform the service you paid for.
And in fact, there are dishonest buyers who track d.c. and if it doesn't update, they take advantage of the negligence of USPS and they claim non-receipt.
It happened to me several years ago. I sent an item to a buyer (who also happened to be a reseller) who claimed non-receipt. Since d.c. didn't show receipt, I knew I'd lose a case so I just refunded her. In this case, I was pretty sure she'd received it based on the way she worded her messages.
So I added her to my "favorites" and watched her listings. Sure enough, 18 months later, she listed the item she claimed not to have received. After several back and forth emails, she finally admitted what she'd done and reimbursed me for the refund she received.
Although my experience is not common as most buyers aren't resellers, it's just one example of how a dishonest buyer knows how to work the system.