Kretha, those cards, licence and mobile would have been transferred to my pockets, they most definitely would not have stayed behind in my pack. First time I've heard of stuff being taken on the hill, though. Was it far from "civilisation"? I mean, if it was a fair walk from anywhere, I would assume it must have been another walker or climber, rather than some opportunist thief hanging around near a car park.
I agree with tonyk, the rest of your gear will probably be dumped somewhere. Who is going to risk being seen with someone else's yellow rucksack? I came across some clothing and personal items (keys etc) dumped over a wall in Snowdonia a few years ago, it had obviously been stolen, there was nothing of any value there. (I put it all in a plastic bag and left it with an explanatory note on the doorstep of the local part-time police station. Was never contacted.)
Mike Knipe, I'm glad you've got such confidence in the police, I hope it makes you sleep easier at night. If the Lakes ones are anything like as useless as the ones in my part of the world, they probably couldn't care less, in spite of what they claim publicly.