I'm going to tell you my own tale of student woe --- just to remind you that, sometimes we proffies actually make a mistake.
About this time of the year, 20 or so years ago, I was a freshman at an R1.
I was in a pretty darned big American Lit class. We had the usual suspects, sweaty undergrads, overworked TAs and a blow-hard, but fascinating professor. It seemed like college to me.
Because I was kind of a smart little cookie, and because I'd had a good high school education that covered much of the material in the class, I was doing well. I was headed for my first college A and knew it.
One day, it snowed and I was a few minutes late to class. It was the first snow, which causes everyone in my home state to lose all ability to drive -- and around the R1, it was even worse.
On the board it said "Final exam, Wednesday, 1:00" -- Dr. Blowhard was lecturing and I took my seat. I wrote down the words on the board, like any good little freshman -- and was relieved to know when the final exam would be.
Fast forward to Wednesday at 1:00. My little freshman self shows up ready for the exam -- only to find another class there.
In my panic, I ran into someone from my class -- who asked why I'd missed the final the day before. This person explained the evil that is the final-exam schedule... something they either didn't cover in orientation or I'd somehow missed it... Remember, this is the first quarter for me -- and all my other classes ended with final papers with due dates on the syllabus.
I consult the syllabus looking for the final exam date -- which wasn't there -- but I do find the Blowhard's office. I go over there, only to have Dr. Blowhard not believe my explanation. He told me he thinks I made it up to get extra time.
The final was worth 35% of the total grade -- my A was now a D.
Moral of the story -- don't be a lazy-ass like Dr. Blowhard -- and the prof before him in the room-- ERASE the board.... and realize that it is possible for you to make a mistake.