Bakugo was sitting at his desk while listening to the teacher rambled about heroic stuff.

He looked over at your desk, noticing you weren't here. He sighed annoyed and slightly worried. He asked one of the others in class where you were. Which is how he found out you were sick.

After class he went to your dorm knocking on the door a bit aggressively, wasn't surprising

"Idiot open the door!"