HAaahaaa, When I did the scheduling for some 50 people ( 100 in the busy season) definitely scheduled to cover "sickness" espeically the Monday morning hang overs!! ANd THAT was the busiest day of the week. I always scheduled an extra person.
Obviously you keep records . . can you find a solution other than you covering??
My solution was, "I'm at home, figure it out." I so rarely get leave so leave me alone. I usually have to donate leave each year so that I don't lose it. This year we're looking like we're fully staffed for the most part, so I'll be able to take more of it.
It takes a lot of evidence to prove sick leave abuse. I almost had one girl for it, and then she saw the writing on the wall and stopped doing it. Success!