The file that the dictionary was using to search for words containing a
specific n-gram was incomplete. Despite being named allWords.txt, the
file is missing many common words, for example I noticed this deficiency
when I searched for words containing "tion" and it turned up only
"himation". So, for now I'm using the "words.txt" file in
jsan_resources, which seems fairly complete (>235,000 words), although
as a consequence of this searches for most common bi and trigrams take a
second or two to complete and usually turn up far more words than any
sane person anonymizing a document would want to look through, so there
are probably improvements to be made to filter the results and/or reduce
processing time.