The same thing happened to me. I created a yelp account for the express purpose of reviewing a local business that has food that's beyond shitty. I wrote a scathing one star review, and it was put in purgatory. Only when I logged into yelp was it visible.

Now, I can understand why they'd be wary of an account that only posted a single negative review, but if you ban someone, you should let them know.