Doesn't sound like a 'stock' app and more like a customized image generator or keyboard. If it's the latter, you might need to select that as your input method.
That's odd... I looked it up and it's definitely an app (they call it a game) , so it should show up in the app drawer. If you find it in the App Manager (Settings/Apps), does it have an Open button? Maybe it has a different name/icon?