It could be that it was flagged as fishy, since the person created an account and left just one positive review.

I've seen complaints about how Yelp filters reviews from new accounts, and how it may more heavily impact companies where it's a one-time service with large fees. I'm thinking specifically a complaint someone had that a moving company had a bunch of poor reviews that were filtered. The reviews were left by people that were so frustrated with this company they created a Yelp account solely to warn other people (because this was a high-dollar purchase, unlike just a meal out at a restaurant), they were legitimate reviews, but looked suspicious to Yelp's algorithms.

No solution for you here, but a possible explanation.

And Google has additional ways to identify sites all related, such as everything in the same GWT account, sites having the same Google Analytics master account, etc. Doesn't mean they use it for ranking, but they have ways beyond just IP to see things are related.

Xenu looks good to me for that page as well. I'd do an-demand crawl for that page/site from http://pro.seomoz.org/tools/crawl-test and if it's still showing up, send an email to help@seomoz.org so we can look and see if there's an error in the crawl software.

Thanks!