Warning for Delay?

[rbruno]

Team A scores to pull within 2 points of Team B with 13 seconds left and the clock running. After the score A-1 knocks the ball away and it rolls about 15 ft to a back wall of the gym. I held my whistle for delay as it seemed an unfair advantage for Team A to stop the clock to issue the warning. As I wait for Team B to go and get the ball, Coach of team A starts screaming for me to start my 5 sec count.... I blew the whistle and told coach A that his team knocked the ball away etc. Of course Team A steals the ensuing throw in and hits a three pointer at the buzzer to win the game. I know I probably shouldn't have blown the whistle here, but how would you guys have handled this end of game.