Unusual Balk Call

[John L]

We had an interesting call the other day. The pitcher threw to 1st base in an attempt to pick off the runner. He had his foot off the rubber when he made the throw. The first baseman was not standing on the bag but was about 6 feet away. When the throw was made the firt baseman tagged the runner out who was standing to the right side of the first baseman. The umpire called it a balk because the first baseman was too far off the bag to take the throw. He quoted a IHSA rule but could not produce it from the rule book. I have talked to several HS coaches, college coaches, expros and some say this is true but others say they have never seen or heard of this rule. What gives??