So as for what the proper ruling should have been… If the error was noticed before the 5th roll of the game, the missing checker gets put back on the midpoint. If the error was noticed later, then the director may not impose a correction, but should explain to the players that if they both agree, the checker may be put back on the midpoint. If the players do not agree, then the checker remains out of play for the rest of the game but is not considered borne off for gammon-saving purposes.