Pre Order Succesfull without client paying

Hello,

I have noticed a bug in the functionality of the plugin. When having in the cart a preorder item, click on the payment system, and you get redirected to the payment system page to add your card details and pay. But instead of paying we pressed back on the browser tab, and instead of the order being canceled the admin and client received an email that the preorder of the product had been successful why?

Can you help to resolve this?

The page I need help with: [log in to see the link]