A few times in recent matches I've had opponents fail to call "not-up" on themselves when the ball visibly bounced twice. I'm pretty sure these were all honest mistakes (I find not-up to be a tricky call, as I'm more focused on getting my racquet on the ball than on seeing whether or not it bounces). And I didn't say anything to the opponents about them. I'm wondering how other people handle this situation-- do you ignore it? Do you say something at the end of the point? Do you stop the point? One time I missed a not-up call, and my opponent stopped the point and said "that was two bounces, right?" I was fine with that, but I don't know how others would respond.