We are contacting you regarding a past Prime Video purchase(s). The below content is no longer playable on Prime Video.
In an effort to compensate you for the inconvenience, we have applied a £5.99 Amazon Gift Card to your account. The Gift Card amount is equal to the amount you paid for the Prime Video purchase(s). To apologize for the inconvenience, we’ve also added an Amazon Gift Certificate of £5 to your account. Your Gift Card balance will be automatically applied to your next eligible order. You can view your balance and usage history in Your Account here:
Putting aside why the system is setup that someone’s digital purchase can even be revoked at all which is another topic all together; Every refund I’ve ever gotten from Amazon came in the form of whatever I used to pay for it. So it’s possible that OP bought the movie originally with Amazon Credit and therefore was refunded Amazon Credit.