What you may have seen is a trick play. The pitcher steps back with his pivot foot and raises his hands like he is pitching. The runner takes off and he turns and throws. Some umps call it a balk because it simulates a pitch but I argue it does not simulate many pitchers pitches if they do not raise their hands when they pitch. We used to use it all the time, but when we moved, the umps here all argue that it is a balk because it simulates a pitch even if it does not simulate the pitcher at the times pitch.