You're starting with a false premise. A short story is not so much a story i the classic sense. It is a literary snapshot. In a short story, you are attempting to capture a moment - an important moment - but a moment, nonetheless. Instead of focusing on climax and theme, put your efforts into the actual moment. Think of a person sitting in a subway car. They will see people of all types coming and going. They will hear arguments and tender confessions of love, heated debates and heartfelt secrets. But they won't get the whole story. They will just get, well, the short story.