player coming off bench

[sseltser]

During a boys JV game at this happen and would like to hear thoughts.

About 3 minutes left in 4th quarter after a foul is called, white has a throw-in near the division line in their front court opposite the table. I am the lead right next to white's bench. Before ball is handed to thrower a white player leaves the floor. So we can't have a violation for leaving the court. I didn't hear a horn, beckon subs, see subs, or see my partner beckon subs. So now I'm trying to look through the bodies and find out how many players are there. I see 4 white guys (of course) but can't see whether there is a 5th out on the wing near my partner (there is not). Anyway before I can whistle of get a hand up, the ball is handed to the white player. After the ball is thrown in and white is getting their offense set (maybe 8 seconds off clock) the white player realizes he wasnt replaced, gets off his bench and enters the court right in front of me. What made it kind of interesting was that he was in such a hurry to get back on the floor that he incidentally kicked his chair over on his way onto the floor and it crashed down so it may have looked like somebody was angry and kicked the chair if they weren't watching. I blew my whistle and signalled a T. When going by the coach to report, I told him that it had to be called and he said "I didn't see what happened." I now realize he said this because he thought it was for unsportmanlike behavior, not entering the floor.

My questions:

Who gets the T in this situation? I am inclined to think the player who entered the floor based on 10-4-2. I also think this should also go indirectly to the Coach because he did become bench personnel. And it would also be a team foul.

Should I have killed this ASAP when i realized there were only 4 whites?

Do I go back to tell the coach what happened after reporting this? He didn't have any questions or wasn't trying to get my attention.

When reporting a T (this was my first) what sort of things do you have to make sure you tell the table? I think I kind of rushed through this part of it.

Are there levels where you try to not penalize this action because they are just learning the game?

Thanks
I look forward to hearing some responses to help me.