[greymule]

I've had only one call like this in my career, and I blew it. Batter hit a sharp grounder off the pitcher, and the ball deflected a few feet across the 1B line into foul territory. The pitcher was chasing down the ball and, it appeared, would have time to pick it up and throw to 1B ahead of the runner. But a little more than halfway up the line, runner and pitcher collided. Each player was slowed, but nobody fell to the ground and I let play continue. The pitcher grabbed the ball and threw the runner out by a couple of steps.

It seemed to me that even though the ball had rebounded a considerable distance, and was probably somewhat beyond a step and a reach when the contact occurred, it was lying motionless and in the imminent possession of the fielder, who still had plenty of time for the out. Therefore, not OBS. And since the pitcher in fact got the out, I didn't even think of INT. But with the collision, it should have been one or the other. Very hard to say which, however, but probably OBS.

I didn't get much of an argument from the offensive coach, probably because before the contact, the play was developing into an out.

This play has one (probably irrelevant) difference from the OP, in that no one could say the pitcher flubbed the hard shot back at him. You wouldn't be rewarding the defense for making an error. It was actually a nice play.