I had this problem. I won't be able to take Latin 5 before school ends. I'll be stuck at 4. Was not happy for a while, but nevertheless I'll be glad to be done.
Happens to me every semester. Two years ago I came up with a course plan of what I would take EVERY semester until I graduated. Spent at least a week on it so I can simply to my advisor and be like "Here's where I am now. Let me sign up." And every goddamn semester, something changes (this semester, my Latin American studies teacher decided to teach abroad. It's a sequence class so that screwed me this semester and next semester).