Firstly you haven't been scammed by eBay rhey are a selling platform, if they receive tracking from a seller showing delivery they have to believe the postal / courier system ( seller pays extra fro this service), that an item was delivered.
As a buyer you can only have 100% feedback, sellers cannot leave negative feedback for buyers.
Signatures are not neccary on items, but tracking numbers showing delivery is what is accountable.
What exactly has happened please come back and tell us.
