I've seen it happen on before, where a different image shows up, but OMG...that was terrible!
My picture was of Barney Fife to go with the "Nip it in the bud" comment from the article. The pic showed up fine in the preview, but definitely not after I posted it.
I hit the "report abuse" button as fast as I could to get it removed.
When the picture is in preview, what I do is hit the refresh button on the browser to refresh the preview page. This will usually catch anything before you post it.