How can I know if a user received a refund for non-renewing subscriptions

Question

In Technical Note TN2413, under How do I use the cancellation_date field?, there is a small note:

Important: cancellation_date is not currently added for consumable and non-renewing subscription products.

However, non-renewing subscriptions do have the option of being cancelled by Apple and the user receiving a refund. I'd like to block off access to my content if the user has cancelled their subscription. How can I do that?