When your absentee player comes back you will have two choices. Either you ask your new player to surrender and your previous player will be able to join, or you could get your new player to use the Name a Substitute option on the Active Games display, in which case the previous player can then play out the rest of the game. However if you go the second route (which avoids someone getting an unnecessary surrender on their stats

) then when the game finishes the result will appear as for the substituted player - when you use a sub, the game still 'belongs' to you. But for a Friends game I don't see why this would particularly matter, so I would advise the substitute approach.