Yes, you should go talk to the shop's owner. They may say you won't get the money, but what will it hurt? It's a hundred bucks, and wouldn't it be nice to buy a new bag or rack or ... Of course, they may be extremely apologetic after recognizing the mistake, give you back your money and offer a discount on a helmet or something. just be nice.

I'm pretty sure some of these other responders didn't quite catch what you were saying in your post. You have every right to feel a little cheated that they gave you a higher price than advertised (probably spotting you as a rookie to the bike buying experience). I'm pretty sure any shop that did that to me would lose my business for the future.

And yes, you can haggle, especially on last year's models. They want them gone just as much as you want a bike.