warm-up throws by non-pitcher
 

In a varsity game today, while waiting for the pitcher to return to the mound between innings, the shortstop threw two pitches to the catcher from the mound. The opposing coach tells the plate umpire she has to pitch to the first batter of the inning, since she threw warm-up pitches. I have looked in the rules book and cannot find any rule to support this. And yes, the plate umpire required #6, who had previously been the shortstop, to pitch to the first batter.

You were looking in the wrong rule book, that's why you didn't find it.

Not a softball rule at any level; I've heard it repeated often enough that I believe it may be an NFHS baseball rule, however.

Ridiculous.

FED Baseball - not in the game until the ball is live.

OBR - in as soon as he assumes the rubber.

LL Baseball AND softball - is in as soon as s/he assumes the rubber and throws a warm-up pitch.

And in LL I simply wouldn't see the person throwing the warm-up pitch. No way in hell I'm requiring a non-pitcher to pitch....ever.