During the season, a substitute may bowl high enough scores to qualify for an award. Provisions are made in the rules to ignore substitute scores for awards.
However, once the substitute has joined the league, the bowler is no longer considered a sub and the games bowled as a sub will count for awards.
To force the scores bowled as a sub to not count, go back to the week/weeks the scores were bowled as a sub. Go into Weekly > Enter Scores and use the Override function. Select the bowler and check the NOT eligible for league awards option.