[schoen]

I was assuming the note would be something like

   Dear Dr. Li, I'm sorry to say that I have to cancel our appointment this afternoon because I've been coughing and sneezing all day. I look forward to seeing you when I feel better again.

[contingencies]

Modern Chinese would write 感冒 (gan mao; 'have a cold') instead. Much simpler to remember. Besides, they could send an audio message on WeChat, which functions like a global distributed walkie-talkie, or type it in pinyin, at which point the computer would auto-guess the characters and they'd only have to remember vaguely whether those characters "looked right" with some general degree of confidence, which is exactly how I input them myself. If they really had to write, they'd use the same method on their cellphone then copy the characters over. If the reader couldn't recognize the characters, an OCR system on their phone could do it for them. In short: through technology, this is now a solved problem.