If my pretty uninformed understanding of Facebook is anything to go on young people make "friends" like its going out of style. Basically anyone under 30 that I am Facebook friends with has a minimum of 300 friends, it follows that if they find a phone they would put their number in there to be friends. It's just what young people do. I guess.
I lock my phone, 'cause I don't like the idea of people perviing at my business. Also because I don't want to find out that a person finding my phone wouldn't want to be my friend. If a stranger looked through my photos all they would think was that I was some kind of mother in love with her son with a side interest in flowers and food. Oh, sure, there may be a few aspects of my life they are envious of.
But on the whole any lady finding my phone in an airport toilet would just hand it over and then she'd be the one scurrying off. Not least because she would have inevitably found it in Jetstar rather than Qantas toilets and she'd probably figure I wasn't even good for a Gloria Jean cake.