When restoring a device all apps are downloaded from the App Store, and if there's one app that's no longer available there it's not getting restored. So it's n

When restoring a device all apps are downloaded from the App Store, and if there's one app that's no longer available there it's not getting restored. So it's not simply "upload it all to iCloud backup"; maybe there's some kind of lookup-by-hash of something that fails when the hashed info is sliced or some such.