I spent some time reconstructing the vector to the sun in the Philae CIVA panorama images.
I mostly used the CIVA camera 4 image. It has a lot of objects casting shadows. onto other surfaces
If one can see an object and its corresponding shadow in an image one can construct a plane using the cameras position and the two vectors pointing from the camera to the shadow and its caster. The sun is located somewhere on that plane.
If one has more than one object with an corresponding shadow one can create multiple planes. And the line that is created in the intersection of those planes will point at the sun.
This approah worked very well for that image.
My normalized vector pointing at the sun in the Philae spacecraft coordinate system is [0.0449037,0.68573,0.726469]
Those numbers obviously do not say much so I created this QuicktimeVR:
This image is looking down at philae from the sun. The sun is in the intersection of the three coloured lines that are the intersecting planes seen edge on.
This image shows which shadows I used. (I found the shadows in the vastly better resolved mosaic released by ESA. I then transferred them to this square image.) The green cross gizmos are the shadow/caster pairs and the red green and blue lines are actually the planes constructed seen edge on.