4-42 Throw-in;designated spot

[RefLarry]

Team A has the AP arrow to start the second half. A1 is standing completley out of bounds (designated thrower) next to the referee. The referee sounds his whistle and attempts to hand the ball to A1 but A1 runs on the court (leaving the designated-spot area).The ref places the ball on the gound OOB and begins the 5 second count. A1 never touched the ball OOB. A2 steps out of bounds and completes the throw-in before the 5 second count reaches 5.A2 appeared to be the player who was supposed to inbound for team A. it appeared that he forgot at first. Is this play legal?