If you didn’t allow it to access your email contacts, it’s still a plausible thing. Everything points to Facebook’s person matching methods being very intricate. From things like caching for people who search for your name on Facebook, people who may have mentioned you (without friending you) on their wall, and a host of other tiny little things. Like maybe people in their place of employment are friends with other people from your place of employment, or you’re both employed in a company around the same geographical location in town.
Facebook looks at so many possible little things, it appears psychic. Then the illusion breaks when it hiccups and recommends some guy from Russia you’ve probably never been within a thousand miles of.