Can you miss someone when they are still there beside you?
You can presume that it is the thought that your love one is going away and you will miss them when they are gone.
But what if you miss them when they are still next to you...you aren't assuming you will miss them in the future but right here and now.
Then it comes down to the definition of missing someone. To miss someone is by definition that they have gone away, and hence you miss their presence.
But what if you DO miss them when they are still next to you. Have you just broken the space time continuum?