I missed my class yesterday because I was so busy.  I stayed late at the office and I came home late.    I was in the middle of taking a shower when you were calling me.  I totally gorgot about my class!  I'm so sorry.  Anyway, today, I will wait for your call.  Talk to you then. 

Hi there!  No worries but I was so eager to talk to you yesterday.  But yeah, I know sometimes we miss/forget things.  Let's talk later. Can't wait.

Cee