Polo also allows drafting players from the stands (If someone goes out injured, you've got 15 minutes to find another player.) and I've seen it happen.
Auburn University's football team found itself at halftime without enough healthy tailbacks and had to use the stadium's PA system to page a true freshman from the upper deck stands into the locker room to dress out and play his first collegiate game. Not quite the same thing as recruiting a fan from the stands but still a surprise for him, watching the game with his family in street clothes, and the team to have to go to that length to get a replacement player.
https://www.sun-sentinel.com/news/fl-xpm-1990-09-12-90021306...