Balk on an appeal

[njdevs00cup]

Batter hits the ball to left, misses first base and proceeds to slide in safely at second. He asks for time. The defensive manager tells the pitcher to appeal. He steps on the rubber, in the set position. I put the ball back in play and my partner yells, "That's a balk!" The coach was upset that a balk was called and went balistic when they lost the opportunity to appeal.