You can also try to repair the game , right click on elite > properties > verify game cache ...
You can't verify it if it is "uninstalled." This just happened to me with Empire: Total War. If you install the game, it will see there are files there and only download the ones you are missing. When that is done Verify the install before running it as a double check. Will save you several GB of bandwidth.I'm not sure you can do this if steam thinks it's uninstalled! Worth a shot though!