Batter awarded 1st base?

[hawk65]

High school varsity. The count is 3-1, nobody on base. Next pitch is called a strike and the catcher throws to 1st base thinking it was the third strike and the batter was out. Coach of the batting team calls time and says batter should be awarded 1st base since the catcher threw the ball to 1st. I'm the plate umpire and am not aware of the rule, so I call time and ask the more experienced base umpire. He tells me the coach is correct so I award the batter 1st base. No protest from the opposing coach. After the game, I tell my partner I learned something new today. He says he's certain it is an ASA rule but not sure about NFHS. I can't find anything about this in the NFHS books. Should the batter be awarded 1st base? Please cite which rule this is.