I think you'd have to validate the "doesn't exist and never did" claim. Categories are "created" as soon as the name of one is saved in any page. If a redlink to that category ever existed, then the category itself was created (but not the separate description page for the category, which is what you need to turn an existing category into a bluelink).

This is likely the same issue as T115756: Search suggests non-existent title due to namespace/redirect mixup.