Out of bounds rule

[Ridgeben]

I ran into this last night and would like to hear from you guys.

Two players from opposite teams are going after a loose ball by the basline, player a1 tries to block out b1 from getting to the ball since it is off of b1 and a1 will get the ball on the baseline. B1 leaps over the baseline to try and save the ball. B1 (while in the air) throws it off of a1 who is now standing out of bounds, then B1 lands. The ball was off of A1 but the coach insisted that it still be A1's ball because a1 was established out of bounds and if b1 threw it off of him it was out on b1. Am I missing something, I gave the ball to b1.