Both went to Google Books and did a search for the single word "cliche" in the book, "The Codebreakers" by David Kahn. (Among cryptography fans, this is a monumental (at 1181 pages), and very well-known book.)
It's an extremely clever move and suggests a new version of the Search in a Scope strategy. By searching just within the scope of a book about codebreaking, Benj and Fred both limited the scope of the search in a meaningful way.
Normally, a search term like [ cliche ] is too common (or, in cryptographer-speak, too "high frequency") to be a useful discriminator term. "Cliche" occurs in too many contexts to help find something like "newspaper cliche" used in "writing code."
But by looking only in the text of the book, the word becomes meaningful.
As Benj writes:
Search in "The Codebreakers" (within Google Books) for the term [cliche]. It gives a result on page 799 that is clearly the story in question.
".. past the censor's eye by using the first half of a newspaper cliche as the codeword for the second half, which forms the plaintext..."
However, the full preview is not available, so you'll have to find/get the book elsewhere. Then I tried searching on that text, as in searching on the phrase:
["first half of a newspaper cliche"]
This gives a snippet which contains the name Calloway.
Searching then on:
[newspaper cliche +calloway]
(use the + sign to get the correct spelling for the name without any spell-correction or synonymization) gives you articles on newspaper cliches and the hint that this is an O. Henry story named Calloway's Code.
From this it's an easy step to find the full text, which is available online at http://www.online-literature.
com/o_henry/1006/ and clearly uses the technique described by the original poster.
Fred got there via a slightly different path (by doing a social-search with a reference librarian) who led him to the Kahn book.
Note that if you do this same kind of search on Amazon.com, the "search within a book" doesn't find the term "cliche" as it's a reduced version of the book (not all pages are available for searching or viewing).
But on Google Books, the full-text IS available, even if not all the pages are viewable.
However, it's very clear from the small excerpt that this text has the answer.
The full relevant excerpt (which I got by physically going to the library this weekend) from page 799:
"O. Henry penned a sardonically amusing story about "Calloway's Code." Calloway, a newspaper correspondent, gets a scoop past the censor's eye by usting the first half of a newspaper cliche as the codeword for the second half, which forms the plaintext. Thus, FOREGONE meant conculsion; DARK meant horse; BRUTE meant force; BEGGARS, description. And--sad to say--the journalists in New York understand it."
My copy of Codebreakers is buried somewhere in a box deep in the garage--it's much faster for me to find it at the library. Which makes me wonder why I have all these boxes of books I never refer to. Maybe I should donate them all to my local library... Just thinking aloud here..