It is never what you think. HERE IS YOUR ANSWER. Learning to interpret dreams is interesting. The other person who you could not see was actually you. It was you looking in a mirror. You are on a whole new journey of self discovery. Now I have been thinking about taking fencing lessons. I hope you did not hear me talk about that. lol You are removing the old self and going to learn how to be the new self. ( For example if you dream someone you love is in a car accident. That is not what it means. It means you have a disconnection with that person.) It is interesting read on.
https://thedreamwell.com/2008/08/26/meaning-of-being-headless-or-decapitated-in-a-dream/