Chess - Good call......
I had a similar call last summer in a 16uB tournament game. Same situation, bunt to the pitcher, BR has to veer around F3 as she was running to first base. I signal the DDB and kill the play when the ball is thrown to 1st for the apparent out. Place the BR on first and prepare to explain the call to the defensive coach now approaching me.
His main argument was that the batter was not in the running lane. I explained that the running lane had nothing to do with this play, but he wouldn't let go. I eventually realized that nothing was going to be gained from this discussion and continued the game. Who knows..could be the same coach you had....
