Since the existing API doesn't provide a way, to figure out if a previous purchase was refunded, one way however is to use the Google Play Developer API.

The way to look up a purchase is by purchaseToken and not the orderId, that is currently exposed:

https://developers.google.com/android-publisher/api-ref/purchases/products/get

It appears that the token is actually propagated all the way back to, and assigned, in the transaction instance, being used when finalising. It's just not exposed.

Aside from orderId, I propose to expose purchaseToken as well, in order to be able to get query purchase status via the developer api.

Either that, or provide the same functionality in Purchasing.