Are you sure they are all gone? When I first saved an animated scene, I panicked and thought I had lost all the frames, but I didn't check the animation frame slider thingy (the technical name for it I am sure) at the bottom, when I slid it fto the right I had all my frames back again. Since then, I have saved many animated scenes (some with 300 + frames) and haven't lost any frames. Maybe you could see if they are really still there for you?