Based on a long history of flight and of permanently or temporarily disappeared planes, government computers using Artificial Intelligence and Factor Analysis probably know to three decimal places which option is most likely, and how these likelihoods change with time.
But that Japanese soldier who hid in the woods for decades was probably given a 0.0001% chance of being found alive.
It's rough on the survivors. A friend of a friend of a. . ., etc., committed suicide so I get to see the results firsthand.