When they, too, never phoned home, the engineers hauled out all the failure scenarios and frowned. Maybe the torpedoes bored too deep to call back to us. Maybe they hit solid rock, shattering. Silence is the worst result you can get from deep space. This mix of various human errors and unknowns can instruct us.
Flexibility is crucial.
We are awfully good at fooling ourselves. Comparison with the Challenger disaster are instructive here. In the Orbiter case, managers clung to their models when experience said otherwise. People and their chimpanzee hierarchies will always get in the way of sound technical decisions. Politics trumps physics, usually.