Something similar happened to me recently, I use FB quite frequently and have a dumb punting phone so was really shocked to see a transsexual WG turn-up on my suggested friends list on my work PC !! Shit... Anyway I tracked it down to FB sucking in my gmail contacts, however, I don't have her/his number listed as a contact but dump a whole load of numbers in the notes section of a phoney contact just in case... Looks like it had read the notes section as well and parsed it for numbers!
So quickly remove the link between FB and contacts the settings/account menu. Damage has probably been done now and its all sitting on a cloud somewhere!
