I'm sure there are perfectly plausible explanations for everything that has occurred. But, if I were in the buyers position - I would have gotten aggravated way before he did. And if I had to open a dispute with paypal to get ANY action on the matter - I would not trust what was in that box. I'm sure it was all straight up - but what happens if the carrier scans a package delivered that has a rock in it? If the buyer opens in and says "hey, I got a rock"; it is his word against the sellers. If he hands the box right back to the carrier and says "nope, don't want it" - there is no concern whatsoever and the deal is reversed. Everyone goes their own way.
Sometimes things are good, sometimes they are not. You don't know until you open that box. But way too much stuff could have been done differently over the last couple months for the buyer to have a completely comfortable feeling about accepting that box. The box will probably start being tracked back to the seller tonight and all will be well. That is exactly how I would have handled it in his position. Who wants to have to remember this fiasco every time he gets his knife out to rub it...