Thanks for the reply. But in the real world, this just wouldn't happen. Nobody would walk up to you and ask you to play with them and then say 'sorry, we've changed our mind'. And even if they did, you could go back to where you left off and continue playing (I'm talking practice rounds here).
If you are playing a competitive round, of course you would change your availability, which I do. I still think it could be done easily - just by using the quit and save game module that already exists.