Stripe "Simple" Checkout - detect if close button is clicked

I've integrated Stripe Checkout into my site and everything works great except for one aspect. I use the 'Simple' checkout mode where Stripe renders my checkout button for me. But I see no way in the docs to detect if the user clicks the close button (effectively cancelling the transaction - see image). Is there a way to detect this in 'Simple' mode (as opposed to Custom)?