According to the rules of logic, they have to refund the money to the address you used to deposit and they are chiefly responsible for such issue as they have limited time period for payment reciepts.
These are weird rules in some exchange platforms which one applied, aren't noticed and mellorated by their team ever.
Anyone can lost access to email anytime,this doesn't mean that email is everything in their rules.
You should contact their license provider,may be they can force bitpay to ask clients for documents in such cases.
I totally agree with you, I think they are just trying to find a way to hassle us on our hard earned money. Because they know how easy it is to write wrong email adress, and by that way they refuse to refund them.
If I need to enter the contact & refund email every time I make a payment through bitpay, it means there are no more privacy as they can see which payments coming from the same email adress.
What happened to me can happen to everyone. We should put some kind of pressure on bitpay, I really hate such hassling companies trying to impose their crazy rules and threatening our privacy.