What determines where a ball is inbounded?

First, Welpe's image is upside-down.

Second, I thought this thread said "Who determines where a ball is inbounded?" as was all excited to share my story. Well I'll share it anyway. I was Trail, called a kick ball in the semi-circle above the FT line. C was looking there for some reason and called it too. I point that the ball is being taken out underneath because I am primary, but C grabs the ball and heads to the sideline. I have to hit my whistle and point again. I could tell C was pissed getting shown up but hey that's his fault for calling in my area.