I think I know what happened, the blue object is something that is placed on your farm and it was showing on the extended tool bar. One day I had the extended tool bar open and in the same place was a water tank. However, when I closed it and went to a different farm, it was gone. I went back to the farm I was on when I noticed the water tank and it was there. I closed the extended tool bar and noticed the water tank placed on my farm. The water tank was just showing through in the extended tool bar.
But it didn't look like anything I had on my farm. It was a small blue object. It looked like a manual fertilizer spreader that you typically find in garden stores. I wish I had taken a screen shot.