and this is what you are seeing.
For your "folder" to open in Preview would indicate that you did just that and what you are looking at is a Picture of the desktop with the folder open on it.
Use Spotlight to find the other folder, just enter the folder name, and see what you come up with'
P
While working with a folder of photographs I inadvertently did something that greatly magnified my desktop. I straightened that out but when I went back to the photo folder all the pictures were selected. The folder now looks like another desktop with a dock etc. with finder at the top. On the regular desktop underneath the file opens in preview. Not only can I not deselect these pictures but all commands are frozen.

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