Hi Kemikal! I noticed the problem when I was "editing" pictures in a folder on the desktop. I also tried the same thing with other folders (i.e. in the "library" folder) and the same thing happened then as well.
Good people! I've stumbled upon a problem. I was quick-editing pictures with the help of Picture viewer (essentially just rotating the pictures and then jumping on to the next picture). I then noticed that the pictures disappeared from their parent folder. This happened to about 10 pictures...