Hi Gamezdude.
Welcome to the Norton Community Forums. 
How are you 110% certain that the file was backed up? The only way I am confident that I have backed up anything is to look for it on the backup and get into a position where I can restore it. It would appear that you did not do that. So how have you got your certainty?
If I was looking for a file on my backup I would open N360, go to the backup tab and select "Restore Files" then put the name into the search pane. Another way to do it might be to search the Norton Backup drive.
From what you say I suspect that in fact you did not back up the relevant file. The Norton options can be confusing. If you would like some help on this then let us know.
I look forward to hearing back from you. Hopefully that we can find the file for you but if not hopefully we can help you get better backups in future.