Download this
https://www.box.net/shared/ihf2zmppm3
Open it in preview, select it using cmd 'A' then cmd 'C' to copy it.
Find a patch with the missing icon. Right click in it and use do a 'get info'
When the get info dialogue opens you will see a tiny icon at the top left of the get info, select it so it shows it is selected.
Then use cmd 'V' to paste the Structure gif as the new icon.
That should solve it.