Apple has started removing games and apps from the purchase history of iOS users when a game or app has been removed from the App Store.
Previously, apps were available for download even if the game was no longer available for purchase on the App Store, this has come to an end.
Games affected include The Walking Dead, BioShock and Monkey Island 2. Telltale pulled The Walking Dead to fix bugs as did 2K with BioShock, and Disney has removed Monkey Island 2 because it was too old. Some games were removed while the developers worked on fixes to make them compatible with iOS 9 which impacted a handful of titles.
A spokesperson for Apple told Pocket Gamer
if [developers] remove their apps from the store, they cannot be redownloaded until the app has been resubmitted to the App Store
Now is the time to make a backup of your apps through iTunes for your iPhone/iPad as it sounds like Apple won’t be giving you the apps back any time soon.