Did I Miss Something??

Today was one of those Thursdays where I:
1) got up significantly before the sun
2) snoozed myself another fifteen minutes of shuteye
3) stumbled around the apartment getting ready and eating breakfast
4) barely made it to the bus on time, barely fit into the bus thanks to the hundreds of thousands of junior high kids in there, and barely made it to the university on time
5) hurried downstairs to Linguistique Générale.

All that was normal. But there was no one there. Did I miss something? Not that I can think of.
I must have been at the right classroom. We have class there every week.
I did check the other classroom though (the one where we have Linguistique Comparée), just in case, and it was likewise empty.
The professor's office was empty.
The normal classroom was still empty.
There were no lights on on either floor where class could be.
None of the other students were around.
There was nothing posted on any of the information boards.
It really is Thursday. Yesterday was Wednesday and I didn't miss a day in there.
I did have December 20th written down as one of the dates I had class. I checked my watch and yes, it is December 20th.
There hasn't been a weird one-hour change in time recently. My watch is set correctly for the one last month.
There isn't a strike going on in my university.
The professor does have my e-mail address, so I should have heard about it if class was being cancelled. Plus, it's always posted.

Yet it's a 24-hour course, and I went through my notebook to count how many classes we'd had, and we'd had seven. So there is supposed to be another, and it was supposed to be today. What did I miss?!?