L3 showing that files recently imported are missing

[rickbelcherphotography]

I have an external hard drive with my images.

If every now and then when you open Lightroom you see that a recently imported folder is missing, in the Finder menu go to: Go/Go to the folder/Volumes click on go and delete any folder that does not have an alias icon.  Then restart your computer and it should be solved when you re-open Lightroom.