I would be more alarmed that there were so few people in class now and would rethink whether I wanted to get out of that class if still possible now and take it at a different time with a different professor? Unless it is his first time teaching, I would think the school would be aware of this professor's class size problems and other people may have complained. I'd definitely talk to your advisor. Why do you think your advisor would tell/talk to the teacher? How big/limited in scope is this school? Is this a for-profit school or "public"/properly accredited one?