Just remember, you can respond to negative feedback. Not sure about neutral.
You can respond to any type of feedback, even positive
I am sorry you are having to deal with USPS issues
When I have had issues in the past I have used this form on their website:
http://faq.usps.com/adaptivedesktop/faq.jsp?ef=USPSFAQ&dest=EmailUsI generally get a call back the same day (if a weekday during business hours) or e-mail within a couple of days. If you know which sorting facility it is at, make sure you list that specific one under the part where it asks you where the problem occurred.
The best thing you can do is keep in contact with your buyer and assure them that you are doing as much as possible to correct the situation. An apology and kind word can go a long way.
In the future I would recommend insuring any package that you do not want to take a loss for.
I once had an item get stuck in the same sorting facility for over 10 days that was literally RIGHT next to where the buyer lived. It kept saying depart then processed through and the cycle continued to loop until I filled out that form on USPS's website (I imagined it just going round and round on a conveyer belt getting scanned in and out
). It was delivered the next day.
Another time I sent an expensive textbook (this wasn't on eBay). The USPS tracking number showed it as delivered but the buyer insisted it wasn't and started to get very pushy about it, threatening to report me. I was frustrated with the situation but gave the buyer a refund anyway. 6 or 7 months later I get a package... It was the textbook that was supposedly "delivered" with a note that the buyer never came to pick it up... I seriously just had to laugh at the whole situation.