"You Cost me a timeout"

[Loudwhistle]

BV, A1 drives to the basket and gets fouled by B1. Both players crash to the ground, A1 limps to the free throw line to shoot two. I'm tableside after reporting the foul and A1 is heavily favoring his right leg, first free throw he shoots and misses by a long ways. Coach asks A1 if he's okay, player shakes his head no. My partner throws A1 the ball for his second shot and the coach requests timeout. I call timeout and hurt player limps over to bench and I ask coach if he's going to be subbed out. Coach says yes and then says "you cost me one of my timeouts, you should have called an injury timeout." I said, "if he would have stayed down I would have." "You're the reff, you can see he's hurt, now I've wasted a timeout." I said, " I thought he was going to shake it off!" Any thoughts?