Dunno about actual 'liability' - you'd have to look up the rules on eBay. I'm sure they cover these situations.

I'd say the sender should at furnish whatever information they have to show that it was at least sent. Consignment notes, tracking numbers, and so forth. I'm sure FedEx would be able to help the seller there, as I imagine they too deal with this situation on a regular basis.

There's not much the buyer can do to prove that they don't have the item in question. But since presumably the seller has already given money to the buyer, it's up to the seller to provide information that states that e held up eir end of the bargain (i.e. sent the stuff). Stuff that's delivered with no signature will still have some proof - driver documentation - that the delivery took place.

This takes care of the scenario where the seller claims to have sent something but has only pocketed the money, and where the buyer did receive something but claims that e didn't (hoping to get a refund or another one). This is why it's important for the seller to have good documentation. If the seller can't provide such documentation, then I'd say the seller is obliged to make good on the delivery or give the buyer's money back.

So which are you, gbeer?

Have fun,

Paul

P.S. Do I look like a lawyer? No, I didn't think so.