This Secret Mission is located in the last area of the previous mission. Go back through the doors where you first start Mission 11.

The Blue Orb Fragment is just hanging in mid-air, waiting for you to take it. The only way to get to it is to use the Enemy Step ability and jump off off the Sin Scissors's heads. After bouncing off of them, you then can use Wall Hike off of the wall to get even more height. Eventually you'll get it, but it takes one part skill and two parts luck.