Better to play than not. Everyone needs to chill out about who is doing what or what kids look good. Our kids are 8 years old....just let them play and have fun. Hopefully at the end of the year all of the kids will develop into better players.
Doesn't matter what age. Did the coach explain the situation to the other coach and refs before the game? Was it agreed it would be a forfeit, or that it would count? Did the other team have a second age-appropriate goalie?
If the coach tried to "sneak" the kid into the game, then the forfeit is justified. Live with the consequence, and put a second goalie on the team.
Or it was discussed and it was ok. Then you don't get the result that you hoped so you complain.