You can easily appeal at Absent Fail (AF) result if you believe it to be incorrect . However, this is not high school. At university (well, at least Usyd) they are very reluctant to enter into any negotiation about marks if no obvious error has been made (such as not recording a mark for one of your assessments). They don't normally negotiate, I know this is extremely tough but with so many students, this is the way it has to be. Otherwise you are going to get half of the cohort of a UoS coming to the coordinators trying to talk their way to better results and with so many students this is just not practical.
Also, like Amleops said: if you have been through difficult life circumstances, try applying for an illness misadventure.
