Here is a clip from the Toronto Maple Leafs vs Los Angeles  Kings game.  This ref gets caught sticking his gum on the glass, inside the penalty box. The guy in there ends up taking it off and properly disposing it afterwards.

You know what I’d really love to see? Refs get into a huge brawl in the NHL. I mean it’s gotta happen at least once right? I guess for now sticking gum on a glass will have to do.