Redo on missed call

[CLBuffalo]

Showcase tournament. ASA rules. All teams are 18U. Number of outs doesn't matter. Runner on 3rd. Pitcher starts delivery (separates hands, arm goes back and then forward, stops and does not release the ball). Illegal pitch immediately called. Ball on the batter. Pitcher then throws a legal pitch to the batter. After the pitch the umpire realizes that the runner on 3rd should have come home. Umpire negates the pitch and has the runner come home. Defensive coach is not happy but doesn't go ballistic. Umpire's apparent reasoning is that the call can be corrected and the appeal process doesn't apply, that is, the runner coming home is not an appeal play that was lost after the next pitch.

Please folks, I'm looking for reasoned opinions why this was or was not the right thing to do. The umpire is a good umpire and made a decision, good or bad. The UIC was not called (remember this was a showcase tournament, drop dead times, no winners or losers, no trophies, etc.) and I don't think this was ever brought to his attention. If I ever get in that situation I'd like to know what the right thing to do is.