For my unpublished blog post, I selected a featured image. I somehow wanted to change the image, so I deleted it. It is not at all there in the media library. But when I click ‘add featured image’ it reappears. Even if I try to replace it, the same one keeps showing up.
I was able to resolve it. Seems there is some sort of a bug. I was uploading a different image with the same file name. Deleted both images. Renamed the new image and uploaded it again. It worked!