The Lightroom catalog isn't being used. There is nothing for Lightroom to find. Images are handed off to Lightroom, not Lightroom finding images.
The catalog isn't being used. Not for images. Not for thumbnails.
Ahem.
Did I not mention that the catalog is not being used? Lightroom isn't being used to generate any metadata.
Exactly how I use Lightroom. Works like a charm.
As I mentioned, there is no need to use the Lightroom catalog other than to import the images and then to remove them from the catalog after editing and exporting them.