I don't see anything weird with what happened to you.
Bench players always have preference, so when you win for more than 20 in the last quarter, they play in their bench position. If there is any starter without substitute (in this case your SF) the game engine search for avaliable players, the same if they are reserves or not put in the line-up.
What the injury could have changed is that during the game the reserve1 had played some minutes as SG, nothing else in this case. I guess that with your line-up, the chances to get that extra minute as PF for your bench1 player were almost none.