Dead ball contact: T or not?

[BayStateRef]

Men's league, played under NFHS rules.

Team A has a throw-in under its basket. Before the ball is at the disposal of A1, the trail official calls a foul on A2 for pushing B2. The calling official said he did not know the ball was not live when he made the call.

Case book says intentional contact while the ball is dead is a technical foul. "If other dead-ball contact is not intentional or flagrant, it should be ignored." (10.3.7)

Now what? The foul was not intentional in the rules sense....but the official did not ignore it...because he did not know the ball was not live. Do we say "inadvertent whistle" and administer the throw-in again? Or must it be a technical foul for dead ball contact?