It is difficult to explain because it is difficult to be sure what we're seeing in the photo.
My guess would be that both antennae have been removed (eg. by accident or bird/lizard strike), and that it is the proboscis we are seeing (though it seems to be emerging from between the palpi at a strange angle).
Major deformities can occur, but are quite unusual. You can get dwarfs, bilateral gynandromorphs, etc. (Minor deformities such as colour aberrations are much more common.)
That's a thought; I know what you mean; nice example in photo.
But if that were the case, I'm sure we'd still see the base of the antennae; just my opinion.
I did wonder if the head was upside down - hence the proboscis seeming to come from the 'top' of the head and the antennae being non-visible if they were in the laid-back position. That doesn't work either; the head is the right way up, as one can see by comparison with this nice photo by Alan Lamb
(Note to anybody thinking they can see a broken left antenna: that's the knee of the front left leg.)
Also, whitebutterfly, you might try asking the photographer
- the photo is Copyright Lori Treleaven, 2009
Maybe she has other photos or knowledge of what she saw in the field.