Class is canceled, but don't tell the teacher...

I went to class this morning and I go to pickup the key to the room. They couldn't find the key so they gave me another one but that classroom was already spoken for so I had to go back and grab another. I finally got an empty room with about 5 minutes until class began, and I still don't see any of my students waiting for me outside the old classroom as they usually do. Fine I think, they are tired today they will filter in late. The bell rang and still no students. I called one of them up and she told me the class was canceled today. So my question is, why do all the students know class is canceled but I don't? Waste my time much?