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I suspect that this app has created a folder on the phones internal storage where it has saved alot of files. When you start certain apps and games they create their own folder and then starts downloading app/game data to that folder. If you then uninstall the app/game it will not delete that folder.
Try using a file manager like Astro File Manager to see if you can find the folder and delete it but be careful so that you don't delete anything else.
To find the folder or folders taking alot of space you could use an app like https://play.google.com/store/apps/details?id=com.levelokment.storageanalyser.