Where did you buy the bag? Most reputable consignors have a lifetime authenticity guarantee. If you bought it off of ebay, I would still see what my options are... I guess it depends on how long you've had it (months? a year?). The truth is, you never know until you try. I have returned things under the most unlikely of cirucumstances, even where there were no return policies. Of course I haven't done so frivolously or simply for buyer's remorse reasons, but if something is either counterfeit or or not as described in any way, then you have a favorable case for yourself. It just takes plausible grounds for the return, determination, persistence and being armed with al of the facts and information (receipts, emails, dates of transaction, etc). If you know who you bought it from, you can try contacting them directly if you still have the contact info. Even begrudgingly, some sellers on ebay will realize that taking a return is better than getting negative feedback. If that doesn't work, you can remind them that selling counterfeit items as authentic is a federal offense, and sometimes just being reminded that they have broken a law and could be reported is motivation enough, particularly if it is someone who is repeatedly selling fakes. They should be caught, but they don't want to be. If you're not up for all of that rigamarole, and try to resell yourself, I think you will be fine if you clearly state that it is a replica. Holy smokes, if Rebecca Minkoff hasn't been taken to court for all the Balenciaga and Chanel designs she's ripped off, you're not going to get taken to the slammer for honestly stating that something is a replica and trying to sell it!!
