To help encourage people to return your BB, or whatever you lost for that matter, you can use a "Help me return my lost thingamajig" web site. I have not yet used one of these, but the news articles that mention them do so on a positive note.
You Loose It
Someone finds it.
They call in the sticker on the back of the item
They get a reward.
you get your stuff back for a small "finders fee"
everyone is happy. http://www.stuffbak.com
it one. www.woomerangit
or something like that is another.
I am considering it as I write this.
Of course this only helps if this is all set up BEFORE you loose it.