Umpire Blunder. What to do?

[varefump]

Actual situation that occured in a high school game this week.

One out, R2 on second. B4 with a count of 2-2, swings and misses. B4 remains at bat and fouls off the next pitch. Then B4 singles to the outfield scoring R2.

Defensive coach then comes out and asks the plate umpire why B4 was not out on strikes. Umps get together and rule that it was too late to appeal the mistake. They let the play stand.

Were the umpires correct?

My first thought is that B5 should have been the proper batter after B4 strikes out and therefore the defense could properly appeal batting out of order since a pitch has not been thrown since the improper batter (B4) has completed her turn at bat.