Accidentally pressed a key combination causing images to be hidden? How do I unhide?

Question

I was selecting images to upload to an online photo album, when exactly the selection I had disappeared from the folder. The images are still on the disk. I guess I have accidentally pressed a key combination that causes those images to be hidden. Is my guess correct? If yes, how do I unhide? If no, what might cause those images I had previously selected to be no longer shown, even though they're still on disk?

More inormation: Near the bottom, it says "No active filter". Restarting digikam does not change the situation, nor does a refresh. I am using Digikam 2.8.0.

I have also tried to rename the folder, and to rename all the files, but neither causes digikam to show the affected pictures (after a restart).

Answer 1

The images got grouped by accident.

Now I noticed that at one of the later images, there was a small icon saying 11. By right-clicking, then group -> ungroup, all images became visible again.