What does "search" search?

pond damsel

The captions (titles) I created for my images in iPhoto are imported fine when I use the MacDaddy uploader, but SmugMug's search doesn't seem to work correctly with them, seldom finding anything matching my search term, even when I know there are dozens of captions containing it. I was first wondering if the fact that phrases in my captions (date, location, species name) of dragonfly photos, for instance, are connected by an underline was a factor, i.e., SmugMug was unable to isolate specific words in its search, but now and again it will find a few images, though never all of them. Why sometimes, but not others?
Searching on keywords works fine, but I sure need the option for caption word search.
Anyone familiar with this?:dunno

pond damsel