Player prop bets stand once your player takes the court, no matter how long they play. If your player leaves the game injured, your bet is settled on the final statistics they recorded.
For example: you bet on a player to score over 20.5 points. They score 12 points before leaving with an injury. The bet settles as a loss because 12 is below the line.
For more information, see the General Rules, Tickets & Wagers article.