fielding too many players

Question
Here is a good one that no one knew quite what to do during my 10yr old daughters softball game tonight  It was the top of the third inning when our girls were batting (visiting team) had we already had one out when my 11 year old son noticed the other team was fielding 10 girls on the field and the rules clearly state we are only allowed 9.  Our daughter who was at bat hit a ball to an infielder (or in this case it was actually an extra infielder). The batter was called out at first and then our coach called time and brought the situation of having an extra fielder to the attention of the umpires.  The coaches and umpires conveened at home plate and this is when the other coach admitted he was playing with 10 fielders all game and to the matter of fact had been playing with 10 fielders all previous  5 league games this season admitting he didn't know.  The umpires said all they could do is make the home coach remove a girl off the field and the game proceeded with 2 outs and top of the third?  What is the ruling of this.  I feel we should have gone through with a protest and at the least should have played the top of the 3rd inning over at 0 outs?  

Answer
Hello Rodney,

That is an unusual situation.  I don't think I've seen that.  The fact that he got away with this for a batter or two is amazing, let alone an entire season.  I as a coach would catch this immediately, as I would hope most coaches would.  
I'm not an umpire, so this question might be better suited for one other experts, but I'll tell you what I think should of happened:
The closest thing I could find to this would be a substitution or re-entry violation rule.  In that situation, a player found to be illegal that participated in a defensive play, would be ejected and the batter and all runners would be awarded one base.  Play would then revert back to the previous pitch which would mean the out didn't count.  If the Improper player did not participate in the play, then he is simply ejected and the play would stand.  You may want to forward this to Mark for verification.

Coach Mike