Game Disappeared from App Store?

I play Civilization War by gamezen. There was an error on the home screen of the game, so I did what I do with every other game I've played. Delete the app and go to reinstall it. However, this time I could not reinstall as it seems the game is not in the App Store.

I search the company, I search the name of the game, how is it possible the game can just disappear?

Thanks in advance