The fact that some of you believe that this is not worthy of any police attention because there are other/ more heinous crimes that take place in our society is pathetic. A person was put in fear and was assaulted while on the job. The individual responsible must be held accountable. Where is your sense of empathy? As Bertuzzi Babe said earlier, none of you would be chirping this tune if it were someone you were directly related to, or if it was your girlfriend/fiancée etc,
Seriously, this sort of thing is common in bars and nothing much is ever done about it. I doubt that the police would be too interested in this, even if they were able to find this guy.
Most likely, he won't be welcome in that particular establishment again.
In a bar you tend to have a few 6ft+ men who trained to, for lack of a better term, 'put you in your place' should you act up like that. They keep the workers and other patrons safe and are necessary, especially since there is alcohol involved. Not so much the case for a coffee shop.