Yes, mistakes happen, and no, we don't intend to attribute Saturday night's defeat to a linesman's error. However, it remains a significant mistake and embarrasses the NHL.
In the last minute of the 3rd period, the Canadiens were trailing 4-3, had a power play, and Jake Allen was pulled for an extra attacker. The Capitals cleared the puck from their zone, which is legal when a team has a player in the penalty box.
The referee made a monumental blunder by calling a stoppage of play nonetheless, forcing a faceoff at center ice. Martin St-Louis had to send Jake Allen back into the mix, and the Canadiens lost precious seconds.
The fact is that restarting the attack at 6-on-4 would have taken about 5 seconds, while regaining control of the puck, sending Allen back to the bench, and everything else can take much more time.