You see, the actual, spontaneous, unplanned incident was done nine months earlier by a black girl named Claudette Colvin. She was in the section designated for black people, however, the front became crowded and she was told to move to make way for a white woman (who was actually fine with standing as it turns out, to show how adamantly racist the bus driver was). She refused and was arrested.
Rosa Parks was a secretary at one of many chapters of NAACP and they had seen the incident but they had multiple reasons for not wanting to publicize it when it happened. One was that Claudette