You should never import the same photos twice.
In library, do you still see the folders in the left panel and the previews in grid view?
Are there any '?' on the folders or '!' on the photos in the grid?
What is your OS and version of LR?
I can´t see the folders. Several of them ( on the same harddrive) have disappeared. But I can see them on the harddrive itself.
I have Adobe Lightrrom CC 2015 and I have checked for updates, but got the latest version.
Yesterday I started Lightroom, uploaded the photos, edited them, I saved the Quick collection and saved new photos there. And today is is like I never opened Lightroom yesterday. The old Quick collection is still there and the new ones are not.
LR CC 215.1.1 is the latest version.
If you have imported the photos and are not seeing the respective folders and previews, are you sure you have opened the latest catalog used - just to make sure.
If you open the import dialog and point to the folders/photos and make sure "Do not import duplicates" is checked, are they grayed out or not?
No, they are not grayed.
If you did not rename the photos (filenames), that means that they really are not in the catalog currently opened. I never heard of LR not saving imports and work correctly. I strongly suggest to double-check if you have opened the correct catalog. Search for *.lrcat files.
I dont see the folders. However, you seem to have multiple catalogs that have been opened today, some yesterday as well as LR5 named and not LR5 named catalogs.
You need to get that sorted and make sure you work with the same catalog. Others may suggest not, I suggest to work with one catalog only.
What happens if you double-click on the most recent of the LRCAT files?
What should I do?
I've just told you - double-click on the LRCAT files. Lightroom will open, and one of the LRCATs will be the catalogue with your image information.
O sorry, now I saw I could search via Lightroom. Thank you! I found all the files!!
Can you give me any tip on how I prevent this from happening again?
You seem to have multiple catalog for both LR 5 and LR CC/6 and you have opened each of them recently, within the last 3-4 days.
Lightroom 5 Catalog.lrcat Opened on 9/16/15 @ 21:03 with the size of 177,888KB
Lightroom 5 Catalog.lrcat Opened on 9/19/15 @ 20:37 with the size of 180,764KB
Then the CC/6 catalog which Adobe so oddly never gave a number to as to separate it from older catalog files.
Lightroom Catalog.lrcat Opened on 9/20/15 @ 09:58 with the size of 180,368KB
Lightroom Catalog.lrcat Opened on 9/20/15 @ 10:16 with the size of 212,588KB
What even odder is the LOCK file is associated with the first Lightroom Catalog.lrcat as the LOCK file creation time is 9:59 and you open that file @ 9:58
Then you have even 2 more LR 5 catalogs dating back to May and June of this year. Although those might be LR 5 Backups as LR 5 created the back up files with the same .lrcat extension.
Why do you have multiple catalogs and why are you still opening, and it looks like you are using, Lightroom 5 when you have and you are using LR CC/6?
Having more than one catalog, unless for very specific reasons, and using both LR 5 and LR CC/6 is extremely counter productive. Along with being very confusing to you and to LR. What you end up with is what you are facing now. LR's default setting is to open the last catalog you were using when you last closed LR. If you have one catalog file open and imported images into it then went to File>Open Catalog and open a different catalog then closed LR the next time you opened LR it would auto open the catalog file you didn't import the newest images to.
IMHO it is best to use One catalog and One version of LR. You need to stop creating catalogs and start using one catalog and the most current version of LR. There are systems in place in LR for separating images, Keywords and collections and you can start by separating newly imported images into different folders. Maybe by the date the images were taken, Year, Month, Day.
before today when I actively searched for the right one, I haven't knowingly opened different catalogs. I usually put in an external harddrive or a SDcard and Lightroom opens by itself. How do I do to deactivate (or what it is that I need to do) to only have one catalog? I only use the same computer so I don't understand why this has happened?