Could you look up where the media is hosted, directly on LemmyNSFW or somewhere else. Voyager doesn't seem to show this so you would have to open the post in a browser. Below is a browser screenshot where I posted the same image twice, once by uploading it directly to my instance (https://infosec.pub) and once by linking to the image on an external host (https://commons.wikimedia.org). For reference, the posts can be found at !test@feddit.org.