My supervisor asked me earlier today if I could do a closing shift tonight, because the other guy called out. Considering that is the first Halloween since 2019 that I'm off and closing shifts always give me stress and migraines, I turned down that request and put my phone on “Do Not Disturb” for the rest of my day.
It's one thing to ask someone to help cover for someone, but you shouldn't be surprised if the other person isn't available too.