Out of Bounds Question

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I'm new to officiating and I was officiating a very close game in a gym where the walls of the building were about a foot past the baseline. A-1 had just got the ball from a pass in the corner and was defended by B-1. A-1 had not dribbled, and Team A had a man advantage as some Team B players were slow to get back on defense. B-1 touched the wall and slapped the ball in A-1's hands. I called out of bounds Team A ball. Team B coach was furious, saying "he cheated," he swore that's not what the rules say, and has "seen it more than once before and I'm wrong," finally saying it should somehow be a tech. My partner and I talked and we both agreed on my call. Is there any rule about a player "forcing" an out of bounds?

Also, the most upset I've ever seen a coach about a call in his favor.