Can you take pics of the bag so that the other members can do an authenticity check for you? I am not an expert on Chloe, but there are several members who can definitely help you out- and I know that posting pics will really help (many people don't like to discuss what they look for when authenticating because they don't want the scammers to use such info to make better fakes). One thing that I have heard over and over again is that price is a good tip off. Why would a retailer sell a bag which retails for $1500 or so for only $800 if it is NWT? Usually, if it is too good to be true, it usually is.
Just post pics and I know that someone will be able to help you for sure! Another thing you might be able to do in the meantime is call a Chloe boutique and ask if the serial number is legit. And I would post a thread in teh Seller Watch section!!!!
I truly hope you are just lucky, and did not purchase a fake!!! Good luck!!!!! Keep us posted!