USPS Lost the shipment

Unfortunately, on a recent Astromart sale, the USPS delivery confirmation reported "delivered" however the buyer said he did not receive the package. The buyer lives in an apartment complex, so I am hoping for now that if the item was mis-delivered, or if the wrong person accidentally picked up the package, it will make its way back to the rightful recipient soon. Fortunately the undelivered item is relatively inexpensive. This situation (either non performance by USPS or maybe a theft by someone else??) is the first time this has occurred to me in over 150 AM purchases and sales.

My question is, assuming the package never shows up, is this the buyer's loss??? Is it appropriate for me to say that based on the USPS delivery confirmation I completely fulfilled my obligation? Or should I give the buyer a partial refund and share the loss with him??? What would you do??

Thanks for any opinions or similar experiences you can offer.

Best Regards,
Don

Was wondering if the 'delivery confirmation' was a signature confirmation? Regardless, it is still your responsibility. You knew this was shipping to an apartment complex, where it is a given that delivery problems can/will exist. IMO you were negligent. Time to step up to the plate and own up to your responsibility. Next time don't be so penny-wise and pound foolish.