http://iscoresports.com/

The title says it all.
When the player left,
at BATTING, I selected NO and replaced him with a substitute player

At the end of the game, I had no stats for this player who had to leave after 3 innings
What did I do wrong?
TIA

If you set BATTING=NO, then it sounds like you made the change in the starting lineup. That tells iScore who played in that position from the beginning of the game. The starting lineup is not used for in game substitutions. Take a look at training video number 3 from the link below for some good information on how to properly make substitutions and avoid issues with the starting lineup:

http://iscoresports.com/baseball/training.php

If all your players are batting (no subs), the proper way to account for a player leaving is misc-skip batter each time his position comes up to bat. The app will ask you whether the skipped batter is counted as a out or not.