Whose arm gets bruised in the missile scene of The Hitchhiker's Guide to the Galaxy?

Question

The very end of Chapter 16 of the The Hitchhiker's Guide to the Galaxy says:

The deadly missile attack shortly to be launched [...] will result merely in [...] the bruising of somebody's upper arm[.]
[...]
[N]o revelation will yet be made concerning whose upper arm sustains the bruise.

TVTropes says:

The Hitchhiker's Guide To The Galaxy did this for episode three of the TV series, explaining which character bruised their arm in the attack. (This was the same stinger as in episode three of the radio series, from which it was adapted.) Done at the end of the chapter in the book, as well. The identity of the person who is bruised, however, is withheld at this point, since it was not particularly plot-relevant, and considered a safe level of suspense. As a result, the reveal is tacked on, seemingly as an afterthought.

However, searching through Chapters 17 and 18 of the book (which are the actual missile scene), I can't seem to find out whose arm actually gets bruised. TVTropes says that it was Arthur for the movie adaptation on a different page, but with the major discrepancies between every edition of THHGTG, I'd like to know if it's still Arthur in the book.

The closest I can find is the following:

It was of course more or less at this moment that one of the crew sustained a nasty bruise to the upper arm.

Does the book ever mention whose arm it is that actually gets bruised, or is it one of those dangling questions that Douglas Adams left hanging?

Answer 1

In the original version, i.e. in the radio series, who sustains the bruise is revealed in passing. Everything happens in the third half-hour episode (“fit the third”).

Near the beginning of the episode, as Arthur, Ford, Zaphod and Trillian are approaching the seamlingly dead planet Magrathea, the narrator makes a series of revelations and non-revelations:

The deadly nuclear missile attack shortly to be launched by an ancient automatic defence system will merely result in the bruising of somebody's upper arm, and the untimely creation and sudden demise of a bowl of petunias and an innocent sperm whale. In order that some sense of mystery should still be preserved no revelation will yet be made concerning whose upper arm has been bruised.

Around the middle of the episode, when the aforementioned attack occurs, the narrator lays it on again:

It is, of course, more or less at this point that one of our heroes sustains a slight bruise to the upper arm.

The reveal is at the very end of the episode. Each episode ends with the narrator giving misleading clues about the next episode, then the credits, then often one of the characters saying one line which either adds to the humor in that episode or provides another tantalizing clue for the next one. In this episode, that final line is

I'm sorry, but I'd probably be able to cope better if I hadn't bruised my arm.

Oh, and that line is said by

Arthur. (But who else would suffer such trivial mishaps?)

The book retains the forewarning and the description of the actual incident, but not the reveal. I see that as a follow-on meta-joke on the suspense created about such a trivial incident.

The bowl of petunias and sperm whale, however, turn out to have a significant effect on Arthur's life later on.