OK. Quick update. The camera has been received/assessed by C.R. Kennedy in Melbourne and they have decided that the camera needs to go back to Pentax in the Philippines. They are of the view that checking the mount alignment (and ensuring there are no other issues with the body) can better be done there. I think Pentax also want to see it themselves so that they can take the issue up with their shipping providers...
In the meantime, they are sending me a loan camera (which they indicated, when I initially wanted the shutter to be replaced, wouldn't be possible; I suppose there's a greater wish to
make things possible after I have the camera was damaged!). There will be no charge to me. All of this seems like reasonable handling of the issue.
I have indicated that I remain worried, even after the repair is done, that other problems might eventually surface due to the knock my camera received. C.R. Kennedy have indicated that they think that unlikely, but that they would take responsibility for that if it arises. Of course, I would rather have a new replacement camera, but I am willing to take the chance and see what happens. However, if anything else goes wrong that could in any way be attributed to this knock, I will certainly change my approach, insist on a replacement and make a much bigger fuss than I have so far. I realise some of you believe that I should be pushing for a replacement camera now; I see this point and thank everyone for it. However, given the provision of a loaner, their ongoing willingness to take responsibility for issues that arise and the very helpful support I have received from C.R. Kennedy throughout, I am willing to accept their approach for now. But my attitude will change if any other issues are experienced as a result of my camera being badly bashed.
The main thing, which no one can ever resolve, is that I will receive the loan camera just after two perfectly clear nights which would have been ideal for astro photography. Not just normal clear nights, but the sort of special clarity, all the way down to the horizon, that I haven't seen for years. That is extremely galling... But there's nothing anyone can do about it.
As for everyone's excellent points above about the mystery of how it happened, I am as mystified as you all are. I don't see how this could occur within a proper package. I don't see how it could occur at all and leave the body cap unscathed. And if the body cap wasn't attached at the time, I don't see how it could have been mounted after the damage. I am unable to produce a clear or logical account of what happened. All I know is that it did happen while not on my watch and I am just mightily glad that C.R. Kennedy are taking responsibility for offering me a solution here. They jolly well should, of course; but that doesn't automatically mean that they would. So kudos to them for that.
Looks like I will be back in action in a day or two. Just in time to pine for the conditions I have just missed!
Thanks to everyone here for your most excellent support, advice and empathy
P.S. - to BL: this
is my camera - the serial numbers match, so I can't escape the issue that way. But thanks for the idea - good one to check!