I dont understand why it has got to be an issue that has to be dealt with by a supervisor? Why can you not just ring Michael, his number is on the board, and ask him what he is playing at. I am quite certain he will apologise and be round to mop the steps.
He generally takes pride in his work but like everybody he does make mistakes. I think he likes feeling part of the community at RQ and constructive feedback from people has got to be a better way to deal with this then a supervisor giving him an ear bashing?