A Play I can not find in rules or case... Actually happened.

[Self]

I am hearing so many different responses to the below situation from HS officials, college officials, and rules interpreters, and I want to get the call right.

A1 scores a basket, as the ball goes through the net B1 grabs the ball and immediately passes it up court to a fastbreaking teammate. The problem is B1 has never stepped out of bounds. Both feet remained inbounds.....

The answers I have gotten are these:

1.) It is nothing, you blow your whistle and reset the throw in with B1 out of bounds. ( This seems strange since it could occur more than once and it seems there would be a procedure to handle this.)

2.) You immediately start your 5 second count since the ball is at the disposal of B1. Then you could have a 5 second count if they do not bring the ball back and throw it in correctly. ( The problem I see with this is alot can happen in that 5 second count, they could actually score quickly or a foul could be committed, it could really make the game messy.)

3.) You blow your whistle and reset the throw in for B and issue B a delay of game warning for boundary violation. ( Not sure this warning covers this.)

4.) It is a throw in violation. The ball was at B1's disposal, to make a legal throw in the player must be out of bounds, since B1 attempted a throw in it without going out of bounds it is a violation. ( The problem I am being told on this is that there is no rule or case that covers this directly and since B1 never stepped out of bounds the throw in did not begin, there for it cannot be a throw in violation.

I have looked all through the rule and case book and cannot find anything that covers this directly. Please let me know how this situation should be handled and what rule or case we use for it. ........ Thanks...