Restoring IAP Currency (Coins/Gems)

I know there’s the Restore IAP function for when the player purchases an item directly. But what I want to do is allow the player to purchase currency that is also earned in game.
This is causing me problems when the player uninstalls or switches devices, since cloud saves are not yet a thing.
The player would lose all of their coins, including ones purchased with real money. They would also lose anything purchased with those coins, and I cannot restore them because they were not purchased directly.

What would be the conventional way of handling this? I think this would be a problem with any consumable IAP in general.