Can you help me identify this cocoon-like thing? [x-post from gardening]

Found this little cocoon like egg sac stuck on the side of a 5-gallon bucket I'm using as a planter. Does anyone have any idea what it could be? I'm in Louisville, KY, and to give an idea of scale, the length of the cocoon is about 5mm or so. Sorry the pictures aren't sharp, the thing was so tiny! http://imgur.com/a/uNKwN