Sorry for the late reply -- it's a great idea to have a tool that will search screenshot captor comments.
The comments should be in the EXIF field for comments. I think "Description" may be the name of the EXIF field.
To confirm I uploaded an image file to: http://regex.info/exif.cgi
Regarding making a new tool -- i wonder if there aren't already good existing tools for this, since any tool that will search EXIF fields in images should work to search screenshot captor screenshots.
I don't know of any that do it.
From a quick look, I found some gallery software for web sites that can search metadata, which isn't really what I'm looking for.
Viewers that I've used don't do it. (Tried a few and tired of playing with image viewers.)
To be honest, I'm not going to put another second into looking. It's just too painful. In the time it would take me to actually look for software, compare and test, I could write it myself.
If anyone knows something that works nicely, I'd go for that, but I'm simply tired of looking for software and finding that there's nothing out there that does what I want - it's a perpetual exercise in frustration.
Most software does not work as advertised unless the stars are all aligned properly, there's a full moon, no cloud cover, sufficient rain without clouds, and you've got enough chickens to sacrifice.
Yes - I'm migrating to a LAMP stack server... pain pain pain pain pain...