USPS Finally Lost A Package

I've been involved in 800 or so transactions buying and selling, and the USPS finally lost one of my packages.
It was a $12 Ebay transaction, uninsured but with delivery confirmation (label through Paypal). The delivery confirmation shows that the item was returned to sender (me) on July 10 after it was refused by the buyer (she changed her mind before receiving it, and refused the package instead of mailing it back - even though I cover return shipping).
I called USPS "Customer Service" - an oxymoron if there ever was one, and my query was directed to my local post office. "What do you want me to do about it?" one worker said.
Overall, a .1% failure rate is probably not bad all things considered. It's not exactly 6 Sigma but I suppose it's not too bad.
I'm just curious about the experiences people have here with shipping USPS.
It was a $12 Ebay transaction, uninsured but with delivery confirmation (label through Paypal). The delivery confirmation shows that the item was returned to sender (me) on July 10 after it was refused by the buyer (she changed her mind before receiving it, and refused the package instead of mailing it back - even though I cover return shipping).

I called USPS "Customer Service" - an oxymoron if there ever was one, and my query was directed to my local post office. "What do you want me to do about it?" one worker said.
Overall, a .1% failure rate is probably not bad all things considered. It's not exactly 6 Sigma but I suppose it's not too bad.
I'm just curious about the experiences people have here with shipping USPS.
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The buyer emailed me after receiving the chip:
<< <i>i received the memory very quickly however it is not compatable with my dell system on the bottom where the gold keys are my system requires 2 spaces and this one only has 1. >>
I didn't have a clue what she meant by that and honestly, I didn't want to fight over $12. I offer unconditional returns, so merely asked for her to ship it back.
It turns out she didn't even open the package - or she did, resealed it and wrote "return to sender" on the package. Regardless the USPS tracking number said the package was refused and was being returned to sender on July 10.
Maybe it will turn up; maybe not. Currently I'm out $50 for the year - $38 to a NARU seller and $12 for this.
Randy