That's odd.
Usually a seller tries to avoid getting eBay and Paypal involved, since if the seller is found at fault in a dispute, her account gets Defects, which can make it more expensive to sell here.
Was your item shipped through the Global Shipping Program? In that case, the seller is covered once the parcel reaches the GSP plant in Kentucky.
But the GSP has a bad habit of opening and repacking (badly) parcels that are not marked with origin/ place of manufacture, which has implications for duty.
However, the GSP /eBay also put a notice in the repacked parcel that this has happened.
Either the seller sent you an empty package or someone at the GSP plant emptied the package.
There is a third option, but I don't want to get anyone upset.