An injured GK and a troll result are different things.
I never have or use a second GK and of course never had to made a sub.
As a matter of fact, in one game, I hardly managed to win a team with an injured GK (2-1), but I saw many games (or posts) with a team, having an injured GK and didn't accept any goals.
Troll result is something else. It's a fix result, where you roll the dice and brought 1-2 and the other team had 6-6.
Even if you had a sub GK 6*, nothing could change that