Strange Sighting...

We have a planter that sits on a table on our front porch. The husband moved the planter down by our flower bed to water it so as not to spray water on my freshly washed windows. He knows how I don't like that. LOL! A couple of days later he went to move the planter back to the table and there was a goose egg in the center of the plant. The egg was in perfect shape, no cracks or anything. We have no idea how it got there. If you have any ideas,I'd love to hear them.