I started watching right at the beginning of that Sabres power play. We were over at my son's house for a gender reveal party. I'm gonna be a grandpa. Grandson incoming.
It was not seen by the ref; it was called by the linesman. Because there was an injury the linesman told the ref what happened at the first whistle (which was the Tuch goal). It was a dead goal walking before it went in.
I just tripped across this on reddit: A family going into a Ducks game wins a prize from Victory+ (basically the same as MSG Network for the Stars and Ducks since Bally went bye-bye). But the gift doesn't end there; it keeps giving (sound on).