I wouldn't worry about it. I've been in 
situations on YJ where cels looked very much like 
something I've seen in another gallery. As long 
as the seller has strong feedback, there is no 
reason to think he or she is trying to defraud 
someone.

About a year ago, I came in second place on an 
auction, yet the seller sold me the cel anyway. 
Later, I received an email from someone who 
thought I had stolen their cel. Turns out that he 
was the guy who won the auction. When I contacted 
the seller, he said that he had two cels from the 
same sequence and instead of puting the other cel 
up for auction, he sold it to me. So, weird 
things can happen on YJ.