At first I was really mad and pissed, but then I learned that they apparent gotten permission from some artist to sell their works there. I can't speak for the other artist that had their works sold by them as some clam that they did give permission for their art to be sold by them. But I feel that there might be other stolen works other than mine, since they didn't contact me for permission.
Thanks to all of you for contacting me about it, and thank you yuumei for providing the prove and photos, you can check out Her Journal for more photos from the convention: )