I had an interesting experience with Amazon recently. Bought some books at a very good price off the Amazon US site, with very good postage prices, which I assumed to be USPS. Often Amazon US items come up as " can't be posted to Australia", but these were OK and Amazon tracking showed them daily all the way to Adelaide, but they never arrived. When I eventually lodged an enquiry with Amazon, they advised me the packages were lost and immediately gave me a full refund. After thinking about it, ( 2 separate packages a month apart both being lost?) I investigated further and was eventually able to find the actual shipping company in the US, ( not USPS but a shipping company) who advised that the problem was with the " last mile courier" and asked me to contact them directly. The company turned out to be Fastway. When I contacted the local Fastway depot, they happily admitted that my packages were sitting on the shelf, ( for a month) as they don't deliver to my area, as even though I'm under 30 minutes from the GPO, I'm considered rural by Fastway. Although my phone number was clearly marked on both packages, they hadn't bothered to call me, but just listed them as undeliverable, which turned into lost on the Amazon system. Once I gave Fastway a new ( closer) delivery address, they delivered them the very next morning.
So lesson number 1 is: always have a delivery address that all couriers will deliver to, where someone is always available to sign for packages. With some of these new ebay shipping tracking numbers you don't actually know who the carrier is, and it's very difficult to find out when things go wrong.