Sometimes with updates and theme expansions, terms associated with the themes gets obfuscated and you end up looking for terms that you think is there but cannot find.
This article takes a look at rescanning the po files, quickly rebuilding them and then re-generating the mo files.
To enable this, you will need to ensure that you have the localization plugin installed that our themes commonly use. If you do not have it installed you can download it here.
In the install page you will simply look for the theme listling and will also find the rescanning button that will allow you to quickly and effectively rescan the po file.
The rescan button is in the cluster of buttons on the image below that is located bottom right and sits in the center.
After rescanning you will see the missing translation strings that you can translate and generate the mo file from that as usual.