Not delivering on reportedly available online stock

I ordered an Xbox 360 Kinect deal online. The item was listed as one in stock. I paid and the order was shown as being picked. Two days later the order was cancelled with no explanation. When I emailed them to ask why the order was cancelled, they responded saying there was no stock. When I went back and checked the website, the listing had been removed. I believe that the listing on the site was a mistake on their part (i.e. it had not been removed once the deal was over) but I imagine that trying to get them to stick to their responsibility to deliver on goods as displayed online is going to be fruitless. Not impressed with the lack of transparency.