LR remembers where a photos is stored when you Import the photo.
LR says the photo is missing if there is no photo file it can access at the location where it was imported from, originally.
You cannot import a photo if LR already has a record of it.
So if you have imported a photo then moved the photo somewhere else using some OS utility or other program that isn’t LR, then the photo will be missing as far as LR is concerned, but LR still has record of it so it cannot be imported, again, either.
What you’re supposed to do is right-click on the photo or the entire folder of photos if it has a question-mark in LR and choose Find Missing Photo/Folder and browse over to it in the file system where it resides, now, and click Ok, and LR will update the location of the folder or photo within it’s catalog so the photo won’t be missing, anymore.
At least that is how it’s supposed to work. It’s not clear whether you’ve actually done the right-click-Find from within LR, yet, or not.
Thanks, but I have done this in other cases before, so I am familiar with
the method. Unfortunately, several photos (and one entire folder, except
2 or 3 photos I had worked on in LR or PS) were in exactly the same place
on the hard drive (in same Picture library folders) as when imported. They
weren't moved, reorganized, renamed, or touched in any way, so I don't know
why they went "missing." If, then, they are in the same place as when
first imported, one cannot "relocate" them and click ok. This doesn't
work, at least not for me.
I have, by now, renamed, re-imported, etc., but the usual instructions did
not work, which was why I raised the question.
I assume I can just delete the "missing" ones now without creating some