kick ball or nothing?

[Coach Bill]

Ball gets thrown from the frontcourt to the backcourt by the offense. As far as I could tell no one on the defense touched it, and the offensive player knowing that it was gonna be backcourt, just stopped the ball with his foot. Put his foot on top of the ball like he was playing soccer. Then, everyone waited for the whistle that never came. The ref signaled a "tip", and the player picked the ball up and dribbled back up court. I had a pretty good angle and I'm pretty sure it should have been a backcourt violation. But, even if it's not a backcourt violation, it's at least a kick ball, right? Or, is merely touching the ball with your foot to stop it legal?