Two man mechanics.
U1 is in B or C spot. Batter lays down a bunt, which is fielded by F1, who then decides to make life difficult by dropping the ball.
F1 then moves toward the line to attempt a tag of B/R.
U1 has appropriately moved toward the play, and is now set just behind/near the mound.
F1 attempts a tag along 1B line; PU is straight-lined, and cannot tell if the tag is made or not.
U1 can clearly see the tag is missed.
Question: Should U1 provide a signal and verbal indication of the missed tag? If so, what should U1 say and do in the way of signaling the missed tag?