That's happened to me before. Player I was going to sub was sent off for a second Yellow in between me subbing him and the 8 minutes game time it takes for the substitution to happen. The player I sent on appeared in the squad image but the sub didn't happen. I was down to 10 men but could not use that sub anymore even though I had subs left and he hadn't actually made it into the pitch.
KFC Loella
Level 44