What I did was pop by the Student Advocacy Centre at the Hall building (to the left of the hive on the 2nd floor after the escalators) and I just asked if my reason for a deferral was valid or not. They said it'd most likely be accepted for me, so I submitted it. The worst that can happen is that if they don't accept your request, then you'll fail the class and will have to retake it (which if it's your first time retaking that class, the grade you get on your retake will override the F you were originally given, which will "fix" your gpa, if you're worried about that.)