Reminds me of me when I first started school.
I was away the day we learned the number "8".

I was already able to read, write do some basic maths etc. But I could not write the number 8 to save my life. Needless to say, I was devastated. because I was planning on keeping this a secret until we finally learned it at school. Of course, I couldn't come back to class again after being away on "8"-day, just going "Hey, I'm sorry, but how do you write an "8", I missed it yesterday." So I just went with what anyone would do in my situation and put two circles on top of each other, until this method was discovered by my teacher about a week later.

TLDR:
I missed the day when "8" happened.