If you've unintentionally hidden Notify for Spotify from the menu bar, you can show it by locating the application in your Finder (Applications / Notify for Spotify) and relaunching it.
Note: If your version of Notify for Spotify is less than 1.0.2, you'll need to update your application in the App Store for this functionality.
For support or to leave any feedback, please email support@thommeret.com.