On the network drive, if it is Windows Server, there is a 'shadow copy' I think it's called, and it would have copies of work, every so many hours, by date and time. Pick a time at the end of the work day from yesterday and ask to have that filename restored from that time period. This information is time sensitive, so the sooner you restore it the better. After a while, it's gone.
If the network has backup tapes/storage, there should be a copy on the backup from that date.
If it is like the drives I worked with at my last job, that would be my answer. The problem is I don't know if your situation is the same or similar. Good Luck!