Money taken yet you're out of stock?

I purchased a pair of sneakers last week. The money was taken out of my account and I received a confirmation email as well. However, my order status now says "canceled." Upon further investigation, it turns out that the sneakers are out of stock and my purchase can no longer be fulfilled. How can they offer something on their app - it showed that the size i wanted was still in stock - and then say it's sold out?!?!?! That's not my problem, it's yours. I've made a purchase of a shoe that was in stock online. If you've somehow sold out AFTER taking my money, you need to sort this out! Such a terrible experience!