Yep, definitely buy a failsafe. In this case it wouldn't have helped you because you lost onboard power, so I would add a throttle-return spring to your rig also.

But you're right, a nimh reciever pack securely zip-tied down should be your first upgrade. It will also provide a good solid 6V of power. I would suggest the cheap batteries website that advertises here, support our sponsors and buy from them!