IMO, it is a HTBT play. It comes down to the judgement of the official. The official has to judge previous play, the actions that led to it, player's general attitude, intent, body language, etc. BM provided the book material by which a ruling can be made regarding fighting. In the OP, and again, I was not there to see the play, it did not sound as if the missed grab/trip was
"combative" so I don't think a flagrant could have been called. Now, pretend the kid did a giant leg whip, in an attempt to slice the other in half, and missed. Or, swung back with a giant air punch and missed. Those are more combative and worth the flagrant ruling even though no contact was made. So, there is a large gradient of judgment by the official. Let's go to the other side and suggest that the kid was tripped by the hand grab. Again, the official will have to decide how to rule with a lot of factors. Flagrant? Intentional? Common (even though maybe not correct by rule)?

Based on what I read of the OP, I might consider a very strong verbal warning to the kid who attempted the grab. I might notify the coach too as to what I saw and what I told the kid. If the kid attempts the same action again, it seems like a no-brainer to issue a T and no one, specifically the coach, could argue after giving the warning.

Rule 4-19 art 4: "..technical noncontact foul which displays unacceptable conduct." or art 5.

In a couple of situations, they did not even see him trip his opponent. So they missed it in a couple of situations altogether. Nothing to ignore, nothing was called.

Peace