Relatedly:
* an old effort to list missing entries for en.wikt:
<http://thread.gmane.org/gmane.org.wikimedia.wiktionary/784>,
* a recent bugzilla report to get lists of search queries which gave no
results/no title matches, to identify requested entries:
<https://bugzilla.wikimedia.org/show_bug.cgi?id=56830>.
Nemo