Last Known Point (LKP)
LKP may be more useful in some cases than a PLS. It may be the subjects car parked at the trailhead, the abandoned campsite, the verified piece of equipment found abandoned in the woods, the subjects signature in a summit log book. No one actually saw the subject there but evidence and clues are just as good to place the subject at that location at some point after they left on the trip. All these items narrow the search down and refocus it. There may be only one PLS but there may be several LKP discovered as clues are found and verified.