Final answer:
The students realized Margot was still in the closet in the paragraph where Marjorie doubts Bernice would go through with getting her hair cut, signifying they had forgotten about Margot's presence.
Step-by-step explanation:
The students realized Margot was still in the closet during the paragraph in which the others learn that Bernice got her hair cut at the barber shop and Marjorie expresses her doubt out loud, thinking that Bernice would back out from the scenario.
The crucial moment when Marjorie's statement made it clear that Bernice was missing is depicted in the line: "Out of the group came Marjorie's voice, very clear and contemptuous. 'Don't worry-she'll back out!'", indicating that the group, and particularly Marjorie, had lost track of Bernice's presence, relating to the larger story's context.