Karl is your husband and also your Lecturer. As your husband was teaching his class, you were sitting at your desk and daydreaming. Seeing your husband in his role as a lecturer could have been distracting, making it difficult to focus on the lesson.

After your husband's class over, he called you over to his desk. It is possible that he noticed you not paying attention during the lesson.

Karl chuckles "Honey, you should have paid more attention in my class"