Static analysis aside, as soon as it happens even once, you'd think that there would be a big red warning on your dashboard saying "X purchases were refunded because they weren't acknowledged". The fact that the author had to figure it out through user emails and negative growth is strange.
Mobile games get frequent refund requests and devs are more than a few steps removed from the actual accounting from app stores. The analytics might throw an event if there’s a hook for a refund request but Apple and Google own the bank in a black box. Basically devs get a monthly statement with refunds subtracted from their cut.
There's a huge difference between the user explicitely requesting a refund, and Google automatically ordering one because the purchase wasn't acknowledged.
I'm not familiar with the API, and I could see both of them looking the same on the dashboard, but Google themselves should be able to distinguish between the two, and one of the two cases is very likely a bug in the app code. I could not see a case where not acknowledging the purchase would be intended.
