Strange occurrence

[mbyron]

The rule is 5.09(g), and the count in the play in question was less than three balls and not a third strike:

(g) A pitched ball lodges in the umpire's or catcher's mask or paraphernalia, and remains out of play,
runners advance one base; If a foul tip hits the umpire and is caught by a fielder on the rebound, the ball is
"dead" and the batsman cannot be called out. The same shall apply where such foul tip lodges in the
umpire's mask or other paraphernalia. If a third strike (not a foul tip) passes the catcher and hits an umpire,
the ball is in play. If such ball rebounds and is caught by a fielder before it touches the ground, the batsman
is not out on such a catch, but the ball remains in play and the batsman may be retired at first base, or
touched with the ball for the out. If a pitched ball lodges in the umpire's or catcher's mask or paraphernalia,
and remains out of play, on the third strike or fourth ball, then the batter is entitled to first base and all
runners advance one base. If the count on the batter is less than three balls, runners advance one base.

To see how that should be scored, check scorekeeping.com.