Subfolder "2009" exists in my Original Photos folder. All the images are in Lightroom. The subfolder 2009 is not visible in my location list but when I try to create it, LR says it already exists. Yet it (out of over 1000+ subfolders) is the only folder not visible. Thoughts?
Lightroom Classic is not a file/folder browser. It shows you the folders it knows about in its database, not the folders that exist in your operating system.
Most likely, the photos in that folder are in your LightrooM Classic Catalog, but in a different folder (this can happen by accident if the wrong import options are chosen). So, you need to search for one of these photos by first clicking on All Photographs and then searching by file name. Once you find it this way, you can figure out which folder the photos are in according to Lightroom Classic, and then even fix the problem, if desired.
When I search the image in LR "Photo" Show in Folder" it takes me to folder 2009. When I ask Finder to "Show in Enclosing Folder" it shows me Original Photos. Everything is correct except LR will not show the folder.