An Adobe support person did what people in that ‘country which cannot be named’ typically do. My case is complicated by the fact that ID was refusing to start a few weeks ago. Apparently, the files that were in folders connected with older versions of ID weren’t moved over. Doing a search did turn them up on my Carbon Copy Cloner (bless its developer) in a folder Library ▸ Application Support ▸ Adobe ▸ InDesign ▸ Version 12.0.
Indeed, where they should be is a folder called Version 15.0.
All my custom-made GREP scripts aren’t there. The same here, Valentina Truneanu, and on my Mac no less.