What happens to one-off In-app purchases if an app is removed from the App Store?

I'm always careful to keep my own private copies of iOS *.ipa files so I can re-install an app onto my device (with the same Apple ID, of course) in the event that the app is removed from the Apple iOS App Store. This seems to happen to games an awful lot, I note (Electronic Arts, I'm looking at you).

I have a policy of refusing to buy Free-to-play games that use In App Purchases (IAPs) to replenish some consumable in-game currency (e.g. "$1 a gem. $50 - Bucket of gems. $99 - Mountain of gems."), so that means sticking to either entirely free (often ad-supported) games and apps, or pay-up-front games.

Lately I've noticed a lot of apps (and games) I've got are sold for free but have one-off In App Purchases, usually to disable ads, or unlock premium content (similar to how 1993 Doom gave away Episode 1 for free via shareware, and sold the other 2 chapters at a price).

However I don't know what happens to these IAPs if the original app publisher removes their app from the store. If I were to re-install the app via the *.ipa file and use the "Reactivate previous purchases" feature (assuming the app has that option) would it work? What happens if it fails? Would I be entitled to a refund if it didn't work?

Recent Questions...