Weird situation

[summdawg76]

After Team B causes an out of bounds violation in Team A's front court on the end-line with 2 minutes remaining in the 4th quarter, the coach from Team B calls a 30 second time-out. The officials move to the teams when the 15 second warning horn sounds and communicate, first horn. Team A is ready before the 30 second horn sounds as it is their ball in their front court on the end-line. Team B breaks the huddle just as the second horn sounds and the Lead official waits until Team B is ready before administering the throw-in. The Lead official makes eye contact with the Trail and Center official and them blows the whistle and gives the ball to A1 for the throw-in. Just after the ball was inbounded to A2, the coach from Team B realizes that B5 is sitting beside him and stands up and grabs B5 and tells B5 to get out there. B5 runs from in front of his team bench onto the floor and A2 who was dribbling near the Mid-Court line has the ball stolen by B5.

What is the ruling here?