I haven't had that play happen to me yet. That said, if the player is leaving the lane, I would not call that. If the player stayed in the lane, with no awareness of the situation, or, worse, is in position to catch a pass after staying in the lane, I will call it. If I see a player standing in the lane, I usually say "lane" as a reminder. If I have to say it twice, and the player does not leave, I then call it.