Bunt attempt....strike?

[just another ref]

Situation: high school semifinal game, player has squared to bunt, pitch comes in behind him, he arches his back and lunges forward, made every effort to avoid the ball, but it grazed him in the lower back anyway; umpire awards him 1st base; coach comes out to argue; We couldn't hear what he was saying, but from his gestures he apparently was asking for a strike, showing that the batter was in a squared position, bat extended over the plate, never pulled it back, etc. Question: What defines what is a strike as far as a bunt attempt. My understanding was that you could do anything you wanted with the bat so long as you pull it back to your chest before the pitch arrives. I'm sure this is oversimplified. Also, in this particular situation, the pitch is behind the batter, he is obviously scrambling forward in his attempt to avoid the ball, so when he switched to the "avoid the ball" mode, does that make the location and movement of his bat irrelevant, or what.
Thanks in advance for your help.