Severus just crossed his arms and shrugged. "I had duties to do, Minerva. I had some potions for the hospital wing to brew and I believe that you don’t want to tell Poppy and the other healers, how to run the hospital wing. Teaching duties. When the note arrived, I was in the middle of a class, so I had to stay to finish the class and I wasn’t finished with the schedule halfway and none of the other teachers were able to replace me during my time. And I had head of house duties, even though I am co-head, I still have to solve many issues with the Slytherin students."