God I hope you'll be able to work out something, but I remember once I bought a Muse at a Department store in Paris (like I said in another thread it took me a few hours to realize the bag wasnt for me) and I went the same day to return it only to their St germain flagship store, even with the receipt they wouldn't return it I had to go back to the Dpt Store...
Then again, I think this was a stock issue for them, they'll probably be more pliant for exchanges especially in your case since there''s a price difference...