Find a different word FTLT. Cheating implies an intent to deceive to gain some unfair advantage. If you are on a break away and I hook you down to prevent you scoring, it is not cheating. It is specifically provided for in the rules that a penalty will result, and in that circumstance I have likely had time to make a judgement about whether I would rather let you shoot or take a penalty, and simply have chosen to take the penalty. It's even referred to as a "good penalty" in some situations. But it's not cheating.
In the case of a goalie throwing his stick, it is the intent of the goalie to stop the puck, not to deceive anyone. If I am caught out in the corner and wheel my stick ninja-style to the front of the net intercepting a puck, I am not deceiving anyone, or even trying to. I am simply stopping the puck. Period. The rules provide for a penalty in that case and it is up to the officials to apply the rules.
In the case of Rumpel, first of all, I have seen him drop his stick several times while simply watching play in the corner. He wields his stick lightly, like a magician holds a wand, not like a barbarian with a cudgel. In the split second that it took for the stick to come out there was not time to even consider his action or if it would be cheating to let go of his stick. He simply was attempting to stop the puck. My opinion is that given the way he holds his stick it was knocked loose, yours is he threw it. Fine. Blame the officials if you think they got it wrong, but don't call the kid a cheater. He's not Lance Armstrong. He was just trying to do his job.
The "grin" that you refer to as evidence of complicity, is more likely attributed to the fact that he said he watched the stick knock the puck wide "almost in slow motion". It was an astonishing turn of events, and no doubt the player at the center of it was even more astonished at the sheer luck involved that prevented the puck from going in. Getting out of it on sheer luck is not the same as purposefully cheating the game, but you are equating the two and labeling Rumpel, who is a fine player and a fine person off the ice as well as on, a cheater. It's a foolish notion and should be stated differently.