Sportscene online

I bought a Nike sports bag online, when I purchased it, it had indicated that there are 5 bags left in stock. I made payments and I have received an email saying payments have been received and my order is being processed. After three days, I received an email saying my order has been canceled and I had been refunded my money. When I check their online, they still have bags in stock and I don't understand why I am refunded. I am not happy with the treatment I have received!!