Phew! Many layers here. Advocating a PLB or other device is good; but as a last line of defence, not a first. The first line of defense is not needing rescue. Not always possible; unexpected events happen; but mostly possible.

Day hikers get suckered in very easily (me too). If it's an even mildly remote area, be prepared to spend the night outside. Doubly so if you are operating solo. The mountains are tougher than you are; there is no dishonour in turning back. Young solo hikers that learn a cautious approach tend to become old solo hikers.

Regarding cell phones: a single pocket of VOX usually means passing through many pockets of SMS (text) connectivity. This can be used to advantage, but make sure you include the current time/date with your texts; they may be substantially delayed between the time you send vs. the time the system receives and relays them. Still, the responsible person who has your "flight plan" will know what to do. You did file a "flight plan" with someone before you left, right?