Pathfinding is a concept in computer science. At its most basic, it's the process of finding a path between two points in a graphical area. A basic search radiates outward from a central point, and maps in an expanding pattern until the objective is located.
This has a great deal in common with the sort of patterns used by search and rescue personnel, expanding outward from a source, searching in an ever-expanding radius, until what's lost is found.
Of course, computing has the advantage of being able to optimize these search patterns. Complex algorithms can account for obstacles, for multiple objectives, for moving targets. Heuristics can account for new information, logical deductions can provide shortcuts. Instead of the long, slow process of treading over and over the same worn out ground, circling the last known location of the objective, a faster, simpler path can be teased into existence.
The shortest path between John and his father takes him 238,900 miles into orbit, which seems an awfully long way from the icy stretch of the Atlantic where they'd all looked for him last. Everyone knows the coordinates. Gordon's got them inked between the thumb and forefinger of his left hand. Scott won't fly over any longer, he'll route around. Virgil will go out of his way to make a pass, if he's in the area. Alan uses them for every password on every device he has. Back aboard TB5, John's system had a beacon hanging over the crossed lines of latitude and longitude, a marker.
With the data that's been wiped from his station, that's gone now. TB5 is a shell, not a trace of John's digital life left.
Doesn't matter, though. There are new coordinates coded close to John's heart, under the shadow of his father's legacy. And in the long shadow his father's always cast, John's been put onto the right track for the first time in three years.