I don't know your implementation, but you could probably save a session variable and check that it exists to make sure people have gone through the correct steps. This is probably something you could also find in the Stripe documentation. I would imagine they would have a way to account for this similar to how Paypal uses IPN and has a verification call back function. This is something I'm sure I could help you with in a premier support ticket if you need help looking through the Stripe documentation and finding a solution.