What you need is a couple of these:
http://www.walmart.com/catalog/product.do?product_id=9192954
Get photos, then post everywhere.
I’d be tempted to sit outside with my gun.
I think it is a crime to have those signs stolen. So you can use the photos to bring charges against this knucklehead.
Okay, so I went out to get my mail and noticed my sign was still there, but my hundred dollar infared camera strapped to the tree by it was missing... LOL.