Final answer:
When Professor Sader didn't show up, another history teacher or a substitute teacher likely taught Ball Customs & Traditions, discussing its history, significance, and practices.
Step-by-step explanation:
When Professor Sader didn't show up, the subject of Ball Customs & Traditions was likely taught by another history teacher or a substitute teacher. In situations where a teacher is absent, schools typically have a system in place to ensure that classes continue without interruptions.
Another possibility is that a knowledgeable staff member or a guest speaker was brought in to teach the class on that particular day. Whether it was a substitute teacher or someone else, the focus would have been on discussing the history, significance, and practices related to Ball Customs & Traditions.