Interference??
 

Pitch is delivered and R2 attempts to steal 3rd. Right-handed B3 steps back out of the box with only his left foot (One foot still in the box), as if to watch his 3rd base coach. In doing so, he unintentionally alters or is hit by F2s throw to 3rd. What is the call?

An NFHS rules cite would be great. Thanks.....

First things first. On BI, INTENT is NOT an issue.

The NFHS rule reference is 7-3-5(b)

Pete Booth

If R2 is retired before reaching 3B, play on. Otherwise, batter interference: batter out, runner returns.

Intent is irrelevant: by doing something other than staying in the box and/or swinging at the pitch, the batter interfered with defense's attempt to make a play.