Tracks Disappeared But Still Play

I was woking on a track yesterday and when i went back to finish it today the strangest thing has happened. All tracks have disappeared except one (which is only a few seconds long). When i press play I can still hear the full song but there is no way of editing it because the regions and tracks are nowhere to be seen. All regions and tracks are gone! Its a mixture of midi and audio tracks. I spent hours working on this for a client and I need to export the stems. Any help appreciated. Never seen anything like this before.