I was a shipper/receiver many, many moons ago. One of the things I learned was to NEVER sign for a damaged package where damage is not noted. Carriers train to try to get damaged packages signed for in good condition because otherwise they are open to a claim. Even a small hole or tear can be a problem.
In Jon's case, the receiver is out of luck because by signing with no notation, he agreed that the package was in Good condition. Disputing that after the fact is suspicious and I would lend no credence to the pictures of the "damaged and wet" package. Perhaps he didn't know what he was buying or didn't ask enough questions - or he didn't like what was inside.
I don't know the why, but Jon's responsibility ended with the signature. I haven't sold on eBay here recently, but even if I was a big seller, in this case I'd take the rating hit because it sounds to me like the Buyer is playing games. It will be painful to try to make a claim, but that would be his only option were I the Seller. Sounds like Buyer's remorse.
EDITED: 15 Mar 2015 12:50 by FIXRMAN