I don't ever recall a player or coach touching a ref and not being disciplined. Maybe you have a counterexample but I have always understood it to be an auto flag/fine.
Now I know this wasn't an aggressive or malicious high five. But according to "the rule", Vince Young should have been flagged and fined. He was not.
Do you seriously not see a player walk up to a ref and put their hand on the lower back of an official while talking to them? I've seen this and no flag was thrown. I've seen coaches on the sideline do the same. It's not a malicious or disrespectful act, so I always assumed that's why they were never flagged. You see players walk into the arm of an official while he is gesturing a penalty. No flag. Even draws a chuckle from some refs.
Accidental, non-aggressive, etc. None of these are flagged. All I am saying is that the rule of automatic flag/fine for touching a ref is not as clear cut as some people make it out to be. To be clear, however, I am not condoning what Cam did. As I said, he should have been flagged for what he did.