> What if all they need is one single person to say hi?
Then say 'hi'. By definition they're not going to seek you out nor are they going to be findable so you're only option is to say hi to everyone and hope one sticks.
edit: heh i hope you're not talking about me, i walk to the grocery store regularly by myself. It's how a take a break from work and get some exercise. i'm fine :)