I have a rather large group playing Year of the Griffon, about 13 players in total, but with mixed attendance. Some just show up every 3rd or 4th session, others have left pretty much, so average we have 4 to 8 there. But I can live with and handle that - it's easier than handling 26 pupils after all. They routinely split up the party to pursue various parts of the three interwoven plots.
And here lies the problem: there is one player that does sometimes not state where he goes (or even goes somewhere entirely different) and when something interesting happens, he declares "Oh, by the way, I am right there and join the discussion/scene/spotlight." When the other players know he was pursuing something different, they usually call him out and he backpaddles.
This "I teleport to the action" is bothering me a little, and while I, as a GM, use some sort of this at times (e.g. officers/agents meeting is called by the commander), or use city-wide alarm to get people to meet up, this part of "I am where I smell action, even if I declared to be somewhere else earlier" seems to break the immersion for some of my players.
How to deal with a player "teleporting" to the action?