I use an image for a page that is uploaded back in 2014 up until now and back then I uploaded few images as well. But when I looked into the library, I could only find the images that are uploaded this year (both in use as well as not used). And yet, in the page editor the thumbnail of that image is still being displayed although I can't select it when I open the media selector.

All images that I have uploaded until now are in folder wp-content/uploads/ as well. Does someone know what is happening?