Hi there!
Long time reader, short-time subscriber and just recently found the forums
Having a blast!
Having said that, I know how much we all like to speculate and how we all like a good mystery to wrap our lobes around - but im afraid I may have to burst your bubble on this one as it is my opinion that this image has indeed been tampered with.
Please dont mistake me, I am not calling the OP a liar, something could have happened between the picture being taken and printed that is genuinely explainable in a different way, this is just my opinion, take it or leave it.
This is the picture moderately exposed. Ive noted this one as the yellow glowing contour that hugs the bodies of the other two people stops abruptly between the womans shoulder and the "disembodied" head.
I believe this I can explain.
Here is a close up of it. I believe this is a feather radius colour OR an artifact of a superimposed blur.
Also, where the "disembodied" head's mouth is, it overlaps the womans ear very slightly.
Number one:
Note the Pixelation at the bottom of this "Disembodied" head. Where the chin rounds, it blurs and suddenly solidifies into a straight line.
Also note worthy is something I cant explain - look to the left of the white box where the womans face should be and you will see two very small, yet precise exclaimation marks.
Number 2:
This I believe is a feather/blur radius - I appologise for my crude circles here - it abruptly stops. There is no gradient fade - it just finishes as if the picture put there is smaller than the origonal it is being put on.
Also note worthy here - look at the womans hair line where she meets the "Disembodied" head - the orange contour is the exposure line, you can see where the head over-laps the tips of her spiked hair.
This is the image inverted (with the circles removed) - it is easier to see the feather/blur radius and the over-lapped parts of her hair. Also the exclaimation marks are more pronounced - if anyone can explain that, let me know, im baffled.
This is the image equalized and inverted. It is easier to see the feather/blur radius and if you look at the "Disembodied" head you will notice that part of the face below the eye socket seems to be missing - it is a little jut that I cannot put down entirely to pixelation.
I believe this same effect can be acheived by using the clone tool in a photo-editing program and carfully trying to place one picture besides another.
This would, however, cause an obvious over-lapping effect that can only be reduced by using the blur tool and tracing the contour of the image. In this case, the "disembodied" head is from a smaller picture, hence why the edge abruptly stops and does not fade into the background.