Players who left lobby not actually gone.

Over the last few days while playing league I have noticed a strange bug. When in a lobby searching for a players (ex.bot/marksman) it is expected that some people will sometimes leave the party. Whats weird tho is sometimes players leave (and everyone in my call of 3 other players confirms they see the same) but they can still talk in lobby chat even tho they don't appear in the lobby and they say they are still on the normal lobby screen and that in fact they never left. If a player joins the party taking their position after they "left" neither player sees the other and they can both talk in lobby chat. This issue can easily be resolved by re-inviting the "missing" player but is a bug none the less.