Generally, for an item with a total cost (including shipping) of < $250, if tracking shows delivery, the seller will win a non-receipt dispute.
For an insured package, if d.c. shows delivery, the post office won't honor a claim.
(Just a commentary: USPS is a PITA to deal with. Even in cases where tracking stops and there's no proof of delivery of an insured package, the post office doesn't make it easy to get paid for a claim. It took me nearly 3 months to get reimbursed for an insured loss and about 3 dozen phone calls and letters.)