How do I make sure that when adding to a catalog PM+ doesn't go looking elsewhere on my computer for other images?
The catalog doesn't look anywhere other than where you've instructed it to look (via operations like a Catalog Scan or Sync). You likely added these files at one point and then moved or renamed the item using software other then Photo Mechanic, and now the catalog has reference to an item at that path in the catalog, but the item at that path no longer exists. You could certainly start a new catalog, which would resolve the issue (because you can't add an item that doesn't currently exist to a catalog), but that's a bit like throwing out your engine when you need to replace a spark plug. I'd probably just find the items that are missing (IOW, they have a yellow dot) and see if you can piece together how they got in that state (e.g. you renamed them, moved them to a different drive, or renamed the folder that contains them), and if you can't, or you already added them at their new path to the catalog, then you can simply remove them from the catalog.
