Who says the camera should be pointing in a direction to capture the probe and the comet at the same time?
In my experience, when you are heading towards something, that something is in front of you. As the probe was (I assume), between the comet and Rosetta, I would expect to see it.
So you are assuming, as in you do not rightly know. Got it.
No, I don't know. We are told that Rosetta is photographing Philae as Philae descends to the surface of the comet. But I don't see a comet. Are you both suggesting that the comet is on the other side of Rosetta? The opposite side to where Philae is descending to???
No, I am suggesting there is a woeful lack of context, but there are a few possibilities:
1. The Rosetta camera was not directly in the comet-philae line and so the comet was not visible.
2. There is some exposure issue with the camera that I am ignorant to.
3. The angular diameter of the comet at that range was too small for the camera to detect.
4. The conspiracy
TM put together a gif of the philae's landing, posted it to the internet and then realized they had forgotten to put the comet in.
There might be more options that I have not thought of at this time.