The link may have been broken because of some technology on the site it came from that prevents deep linking. For instance, you might need to have a cookie from the site to view the image. I've run into things like that myself, where I could still view the image fine on the CardBoard right after I posted it, but others couldn't, and I couldn't view it if I came in via another browser or an incognito tab.
When an img link doesn't work, the board displays the url, or at least the last part of it.
When an img link doesn't work, the board displays the url, or at least the last part of it.