Eeek that would suck. I would assume everyone would leave, because I am sure both the bride and groom would be humiliated and not want to stay and face everyone. i don't think you would get your money back (but every place is different) especially if it has been decorated and you are actually at the place about to get married, I wouldn't expect to get money back, it is not the reception hall's fault that the reception was cancelled. I know it stinks, but I think you would be obligated to pay, there is probably a certain date that you have to back out of the contract by. Best of Luck.