Plot hole: Joy and Sadness are stuck outside of the control center. They are trying to figure out how to get back, and encounter maintenance workers who are discarding old memories. The maintenance workers show that they have the power to send memories back up to the control center to be played. Why couldn't they send the core memories that Joy had back up the same way? Better yet, why not use that method to send Joy and Sadness back up to the control center? The director of the film is even aware of the plot hole, and said "Yeah, well then we wouldn't have a third act," before explaining how the idea of recalling memories was added in later, "box[ing] [the screenwriters] in a corner a little bit."
Question: When Joy is in the dump of forgotten memories, she sees a probe containing the sad memory of when Riley lost a hockey game after missing the winning shot. The probe shows that after Riley felt sad and has been cheered up by her parents, she is cheered on by her old team mates. Joy knows that since that probe is blue, it was a memory represented by Sadness. She begins to realize that Sadness helped Riley to ease her conscience. How come Joy didn't see that before when she would have been at the control panel in headquarters just when the event occurred?John Ohman