BEEN THERE DONE THAT!
That happened to me with an Intro to Mass Communications course my Sophomore year of college. I wasn't positive, but swore up and down that the final was on a Thursday! I went to the class and there was the chemistry class that was always before my class still in their final. I waited and waited and finally went to the Student Center to see if there was something posted on the website.
Finally I made my way to the professor's office and he gladly allowed me to take my final. He even put me in a teacher's room and allowed me to keep my books and everything right near by (without concern). Of course I didn't cheat but I was amazed at his flexability.
So, don't feel so bad. I DOES happen! I'm sure your professor will understand! best of luck (I hate Algebra!)
