on Writing Forward:
Plot points are the events that move a story forward—the twists, turns, and developments that push the characters toward the climax and resolution. Each plot point is a significant moment in the grander scheme of things.
If a character loses her keys as a way to show us she’s absent-minded, then it’s not a plot point (it’s characterization). But if she loses her keys when she needs to drive to the emergency room in a life-or-death situation, then it becomes a plot point.