Perhaps the other hard drive WAS his backup.
You can plan for data failure, but its hard to plan for robbery. Not like you're going to buy a portable HD, toss it in a safe deposit box and get it out once a day to back up your shit.
Now, you could, in theory, encase a HD in a 10000000 pound block of concrete. It would probably stick around. But then you'd have heat issues. Damn it, now we need a 10000000 block of concrete with heat vents. And lots of lazer gun protection, incase a mini Luke Skywalker decided to drop a mini bomb down the heat duct, therefore blowing your Hard drive/concrete/deathstar all to hell.
Back to square 1.