Mysterious Sculpture Sightings

I recently read that libraries have been the lucky recipients of wonderful paper sculptures left for people to find.  The artist is unknown.

What a wonderful mystery to have on one's hands and such a delight to be one of the folks able to experience this in person.

Have you left your art for people to find?  Or if you were doing this, would you find a way to watch the reaction of the people finding it?  Tell us about it.  We'd love to hear your thoughts and or stories.