Ok, so I told you all about the wonderous package mailed 2 weeks after the seller claimed to have mailed the costume.
Told you about calling PayPal and talking to them about it.
Tonight I got an email that the issue was "resolved" because they had gotten proof of delivery. So I called them back.
Again the PayPal person was EXTREMELY helpful and considerate, but explained that legally there's nothing they can do because the complaint was for non-receipt and I did receive something. He did mention in passing, however, that it was too bad they weren't allowed to do anything about mail fraud like this...
And of course he's correct. The empty envelope was mailed in New York State, which means yes, yon seller has committed mail fraud in the United States and the nice postal investigators can take it from here
I have informed yon lousy seller that she might want to weigh the pain of refunding my (very meager) payment over the pain of being fined or potentially even jailed by the US Postal Service and the government. Of course, who knows what the legalities are with it being an international transaction (she's just over the Canadian border but was very careful to mail her bogus package in New York). But I don't care. I'm going to be stubborn.
What a hoot. I can't wait for the next response. I mean, we're talking twenty bucks here and I've wasted more than that in the junk food machine this month. But this was a blatant attempt to get out of something with me and with PayPal, and I'm an evil bean who won't let it drop.
(So if anyone happens to know a lady in Brossard Quebec who sells costumes on eBay, let her know that she should just cough up the refund).

"The permanent temptation of life is to confuse dreams with reality. The permanent defeat of life comes when dreams are surrendered to reality."
James A. Michener, The Drifters