When Sammy sees his manager, Lengel, confront the girls about their state of undress within the store, he immediately notices that Queenie, as he has mentally called her, is blushing. Sammy is attracted to Queenie, and consequently feels an obligation to her. He doesn't state outright what it is that causes him to declare, "I quit," but he does state that the whole time he is ringing up the girls' purchase, he is "thinking." Evidently, he is irritated by Lengel, and his desire for "policy."
When he finally does say, "I quit," he does it deliberately before the girls leave; although, they are in a hurry to get out of the store. Sammy hopes that they will notice his gesture and think of him as an "unsuspected hero." However, the girls do no such thing. Instead, they simply keep walking, and Sammy is left to confront his manager. He tells Lengel that he had no need to embarrass the girls, but Sammy ultimately is left feeling as if his gesture was not worth it and the world would not be kind to him in the future.