Odd shaped object floated silently over the treeline.

My wife and I were attending my daughter's soccer game and about halfway through the game, I noticed a strange looking dark object floating over the treeline. It wasn't moving much at first, but after a few seconds it began to move north. My first thought was that it was a mylar balloon, but it didn't go up. It stayed moving horizontally. I pointed it out to my wife and she stared at it for a while and agreed that it was something very unusual.