It makes sense for a dealer to have flashy things 
at their table to attract customers. I would 
fathom to guess that unless you are a *very* good 
customer of a given dealer, there are still a 
number of cels that they wouldn't offer out for 
sale in advance - even if you directly asked. 
This would probably go especially true for 
something that the dealer figured would be a good 
eyecatcher and/or a fast sell.

I admit, in the past, I have had dealers who have 
been extraordinarily kind enough to offer me 
pickings from cels not on their sites - which 
they had reserved to bring to cons. (Hey, someone 
has to help out Draccie the Conless Wonder. ^_^;;)
But I get the feeling this is a rarity. . .

Many Sharp Smiles,
--Drac