I bought a cel from Noriko's Anime 
(darkharbor.com).  They pulled it and set it 
aside.  My payment arrived.  They couldn't find 
the cel anymore.  It was "just gone".  It had 
disappeared out of the "sold box".  They had no 
idea where it has gone to.

When this happened, Noriko's was wonderful about 
it, and made me a compensatory offer that was 
very kind;  they also shipped an unexpected low-
end "gift cel", which turned out to be perfect 
for the young cel collector that I was actually 
placing the original order for, and resulted in 
great happiness.

(So, I will for sure buy from Noriko's again!)...

These things do seem to happen.  Give them a 
chance to make it right with you, and to work 
something out that will make you happy.

But if they don't take responsibility and make 
things happy for you, then do contact PayPal, 
lawyers, and anyone else who can help you regain 
what you've lost.