I reckon that the B-2 Stealth Bomber is not a secret anymore . . . and has not been a secret for a Very Long Time
As a side note: I once saw a B-2 Stealth Bomber flying at about 10,000 ft over Missouri near St. Louis. Awesome sight - incredible silhouette but what I remember most was the sound. Very strange . . . normally when you hear a sound you look in that direction and can find the object. Not so with the B-2 - the sound comes from everywhere which makes it very difficult to visually locate the plane in the sky.