Hi @blakespot
It seems the original developers registered the fields via PHP. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/register-fields-via-php/. All of the fields registered via PHP won’t show up on the field group editor page; that’s why you couldn’t find it there.
It’s also possible that they use the Local JSON feature and hides the field group using the “private” option. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/synchronized-json/.
I hope this helps 🙂
