Again it's almost certainly other people using their phones. One of your facebook contacts friended this person, maybe even before you shook their hand, facebook is going to recommend you friend them too. I don't friend anyone any more on facebook and the last time I did I lived in another country. It knows where I live now but it has never recommended anyone close by to friend. However, I do get friendship recommendations for folks in the country I moved away from, and I'm sure if I lived there still I'd have actually bumped into said people and thought "huh coincidence that facebook recommended them or are they spying on me?!?!"