Do you usually confer with him and confirm your appointments the same day (in the morning as you outlined)? If that is the approach you are both used to, the pattern you have established, shall we say, then it makes sense that he would make alternate plans if you do not confirm the same day as usual. Like inviting friends over to watch sports... I also make appointments days ahead of time, but I always confirm same day, even for my regulars. People get sick, life happens, things come up. So I consider that pretty standard.