Ok I see now that when SC saves to jpg, tiff, gif, it puts it into the standard "comment" field.
But when saving PNG files, SC puts it into a "png key" called "Description".
So the trick when searching is to search the Description tag (maybe called Caption for some apps?)
For example xnview CAN see the description but lists it under IPTC tag of "Caption".
For example in xnview:
-mouser
mouser, turns out the files I was finding were jpegs:
the info was in the 'description' field.
With PNG files, I still cannot find *any* info from SC's comment box using XnView or Picasa.
With XnView I tried each of the following: Description / IPTC >All / IPTC > caption / EXIF >All / Comment
Now,
I'm not sure I fully trust XnView nor Picasa.
Maybe better to use something that simply shows all metadata for the file.
Using Dopus to show all metadata:
(Viewer >Edit metadata) shows no information for PNG files.
Note it does show the info in description field for JPG files.
That's as far as I've gotten today - and I dont really know where to go from here (any ideas anyone?)