It is not visible because the imageURL and thumbURL both point to non-existant files.
eg, your imageURL is:
imageURL="images/img_9846 no fat.jpg"
... and there is no such file in the 'images/' folder. (You do, however, have a file named 'img_9846 no fat2.jpg'.)
You cannot delete the entry from the svBuilder-Pro interface because the image has been deleted from the gallery manually.
However, to remove the entry, you can open the gallery's XML file in a plain text editor and delete the image entry below before resaving the file:
<image imageURL="images/img_9846 no fat.jpg" thumbURL="thumbs/img_9846 no fat.jpg" linkURL="images/img_9846 no fat.jpg" linkTarget="_blank">
SimpleViewer Support Team