You'd think they'd know better to tell you this when you're around scalding hot coffee, sharp objects, and blunt instriments. Add one disgruntled employee who has been pushed too far and they've got a recipe for a coffee massacre.
Some managers just don't have a sense of self preservation. I'm lucky in the sense that my bosses are so stupid they don't know how to work a phone. Even if they do try to call me in on my day off they mess up dialing and get the wrong number half the time, so I have another excuse not to come in.