Restauranteurs, when you're calling Yelp to ask about missing reviews, RECORD THE CONVERSATION! One recording of a Yelp rep saying something like that is game over.
Yelp has tens of thousands of paying business customers, and yet with all the sensationalistic media play this type of story somehow continues to generate, no one has ever produced empirical evidence of a single documented case of pay-for-play. I'll also point out that there are at least three former Yelp engineers on this thread - some of whom didn't even like working at the company - who are steadfastly defending Yelp's business practices as legitimate and above-board.
By all means, record it if it happens. But don't hold your breath.
Yelp could never manipulate reviews and this restaurant owner could have been told exactly what he claims. The two things aren't mutually incompatible.