All I can say is what I would do and that is I would choose your following suggestion:
"Mark it down with a note about me being sick so I at least have a record? And just try to suck it up and not worry about the gain next week because it is nothing bad & nothing I did wrong?"
Makes sense to me.
Hope you are feeling better
It has been years since I had the flu, maybe those flu shots that I hate actually work. I have been getting them every year.
It is more easy to be wise for others than for ourselves. ~François Duc de La Rochefoucauld