It is definitely difficult to keep up with all of the paperwork when you have an absent kiddo. During flu season, it's even worse, because you may have 3-4 kids out at a time to keep track of.
One of my classroom jobs is Absence Coordinator - usually the students that apply are organized and like to be the teacher's helper anyway, so it makes it easier for all of us involved. They use this sheet to write down the assignments from the morning board. I make many copies at the beginning of the year and then they pull a new one from the tray for each day a student is absent. Any work that is completed that day in class is paper clipped to this sheet so returning students know which assignments go with which day.
This also helps if a student is absent for multiple days and a parent calls requesting homework. It is easy to put all of the paper clipped piles together, grab any texts they need, and send them down to the office.