Defense reaching through plane on throw in.

[Damian]

Basic rules question.

At a camp I attended, I was told this.
1. On a throw in by Team A, defender reaches throuh the boundry plane. Delay or game warning (or T if there had already been a delay warning).
2. Same play, but defender strikes ball while still in thrower's hand. Technical
3. Same play, but defender strikes arm of opponent-Intentional foul.

During a game, I had situation #3 and call it intentional. Partner said it should have been a technical. Looked through rule book and couldn't find situation #3.

Please clarify and show rule or case book reference.
NFHS rules only.

Thanks,
DD