Considering PG didn't strike down the story I presume to think he expected it to leak out or didn't ask it to remain confidential.
Re: "Semantic Scramble", this was/is used quite successfully in a university course I tutored. Students are supplied with Java code featuring a unique comment style (/ * */). So many students blindly copied code out of another student's assignment and submitted it as their own that we could effectively generate a map of the plagiarism without even looking at the code -_-
For images steganography would work easily enough and for "semantic scramble" see "Practical Linguistic Steganography using Lexical Substitution"[1] from EMNLP 2010 =]