A1 leaves the ground holding the ball. While A1 is in the air B1 knocks ball from A1's hand. While still in the air A1 regains possession of the ball and lands holding it. I said this was not traveling since the defender hit it and the ball was no longer in A1's hands. My partner said is was. I cannot find this exact play in the case book. Let me know what ya'll think, and where to find it if possible... Thanks...

If the ball is knocked loose then A1 has lost possession.
Therefore he may regain possession and come down without
it being a travel.

JAR is correct. Player control ended.

Correct! Player control ends on a shot, loss of possession, or dead ball situation. In this case there is no player control, so there can not be a travel. The ball is loose so anyone can recover it. It would be an unfair advantage to have a rule which would allow one player but not another to recover a loose ball.