I could not understand the complete scenario. Is that specific folder there on your EHD and unavailable on your laptop hard drive or is it the other way round?
And if you check the folder structure outside Lightroom, are all the folders properly there on both the hard drives ?
I apologize for the confusion I caused by mangling the important sentence and not proofreading it more carefully before I posted my problem. I should have written "The file structure and contents are the same. In the case of one of my Lr libraries, the library on the EHD doesn't see one of the folders that it should see on that EHD; it sees that folder on my laptop; the other two folders it sees are the ones that are indeed on the EHD."
I did check the folder structure by comparing the contents of two side-by-side finder windows. The structures on the laptop and the EHD are the same.
By the way, subsequent to my first post I opened one of the libraries on the EHD that I had not used in a while and was surprised to see that in the case of one folder out of many, the library saw the folder that is on the laptop but not the folder it should have seen, that is, the one on the EHD. Thus, the problem actually exists in two of my libraries, not just one, and in each case with just one folder.
I keep suspecting I've made an error in my workflow on a couple of occasions and can't retrace my steps. Perhaps I should try doing full CCC clone of everything to a new EHD an see if the problem exists.
Thanks for your continued attention to this.
You haven't made an error. That's the way backups of catalog files work. If you open them, they still point to the original drive. All of this is the way it should be.
If you need to make use of your backup catalog and backup photos, you should copy all of your backups (photos and catalog file) to the original locations on the original drive, and then everything will work. Alternatively, you can reconnect your backup catalog to use the folders on the backup disk by using these instructions: Adobe Lightroom - Find moved or missing files and folders
Thank you DJ.
One mystery to me is why I did not have this happen from the beginning of my established working habits. As I wrote earlier, I do all my work at home on my laptop and clone with CCC each day to an external drive. The Lr catalogs and the original files are in one folder in on my laptop. The EHD has whatever CCC cloned onto it from the beginning of my use of CCC. I use the EHD when I go to classes, where I sometimes create or alter files. When I get home, I do a reverse clone from the EHD to the laptop. This has always worked ok for me, or at least I should say if there are any problems with having done this that create missing files, they haven't come to my attention yet; there are no missing files in the Lr catalog on my laptop.
Until recently, using my main Lr catalog on the EHD never presented the problem of the EHD looking for files on the laptop (I don't have the laptop with me in class). The Lr cat on the EHD and the files on the EHD worked as a unified whole, as if the EHD didn't know the laptop exists. I don't recall ever looking for the laptop to be listed as a volume on left panel of the library mode (i.e. in addition to the EHD itself).
I've found the problem to exist with one folder only in each of two different catalogs, and I'm beginning to suspect (as I wrote earlier) that I made an error in my workflow on a couple of occasions and can't retrace my steps.
Prior to your reply, I did a full CCC clone of everything on my laptop (i.e, all the Lr things, cats and image files) to a new EHD, and the exact same problem came up: when I opened the Lr cat on the new EHD (not the cat on my laptop), the newly-cloned Lr cat saw the newly-clones files that were on the new EHD (as I would expect from my previous experience), except for one folder, which saw the files on my still- connected laptop. As I recall, over the past few weeks, when I saw at school that those files were noted as missing, I imported them at the start of class from the EHD I had with me and when I got home I cloned the main Lr folder back to my laptop. I see now I may have compounded the problem by doing that.
If you've gotten this far after reading everything since "Thank you..", well, thanks again for taking the trouble. I hope I've expressed the situation with optimum detail and some short explanation comes to mind.