Not sure why this is an FML. The school will just have another teacher or administrator proctor the exam. The only way this could be an FML is if the teacher was a lenient grader and now you're worried about your grade.

Ya well after enough lawsuits schools will let you finish your class with a different teacher wasn't like that when I was young, I had an algebra teacher who had a mental breakdown but the school didn't do anything till fourth marking period and they failed all eight of her classes it took a lawsuit from the parents to allow us to retake algebra the next year

Was the teacher gonna grade on a curve or some other lenient grading?

Unless they were cramming everything into your last lesson before the final, this wouldn't have been a problem. If you studied your notes the night before, and didn't lose a lot of sleep, you probably did fine. Or you may have winged it, like I did, and went from a straight A to a solid C student overnight, because apathy is your friend.

you are in high school, it will be fine

don't worry the new teacher or whosoever will be assigned to conduct the exams and grade will definitely consider the series of events and be slightly gracious and rational while grading.. I mean that's what you should think like if you're being optimistic otherwise all hell breaks loose if you're too hung up on your previous teacher.

Why were they fired? It may have been because they were carrying on with a student or such rather than any teaching problems.

8th period??? How long are classes in the states, like 30 mins??? We had 4 blocks of 1h20m each!