Worst experience ever?

Found a shoe that was always out of stock on superbalist managed to get on the waiting list for it. I was notified that it was finally in stock when I logged on it said only 1 left. I felt I was pretty much in luck because I had it... As I'm busy trying to make payment I suddenly get a notification to say my cart is empty now.. meaning someone just purchased it while I was busy paying.. I've never felt so dissatisfied and upset about it. Feel like there should be upgrade to app as it clearly doesn't work. I would need to wait again just to have the same situation.. thanks alot..