This keyword was working on hewiki (general index) before the DC switch on Apr 19 but seemed to stop working just after the switch to codfw.
A possible cause would have been a discrepancy between the indices in eqiad and codfw but after checking the mapping none of the clusters seemed to have this new keyword indexed.
We need to investigate on the possible causes of this problem (check index creation date, ...)

In the meantime we should reindex hewiki and all other wikis that lack this new keyword.

UPDATE
the contentmodel keyword is in fact in the mapping on both clusters (I think I mismatched some wikis when I checked, sorry).
The problem appeared to be a discrepancy between indices. The page User:IKhitron/WLM.json on the codfw has not been reindexed since the keyword was added.
This is known limitation of CirrusSearch:
We have a Sanitization process that is meant to reindex out of date pages but in the case of new keywords the process lacks a way to detect that a new keyword requires a reindex of some pages.