Just before we get off the topic of moveable obstructions I wanted to share this video by Doug at Golf Victoria.  He is very careful to explain the rule taking into account that your ball may move after removing the man made object.  He also says that this covers all man made objects around the course.  So imagine that your ball is up against a moveable object and it does not stay where it landed because of a hillside.  Doug is clear that you discover a spot to place the ball after experimenting several times coming down the hill to find a spot where it no longer moves.  That is where you place the ball.  RULES, RULES, RULES we need to play!