Text on a page gets indexed when you preview.
I discovered this by using (perhaps this is weird) the Sandbox to preview my markup in a file that I was preparing to check in through svn. I just deleted the original Sandbox text in the edit form, pasted in my file, hit Preview, then cancelled the edit, leaving the Sandbox unchanged.
After that, the Sandbox was one of the search hits for terms in the new page, and the Sandbox excerpt in the search results showed text taken from the new page, that was never really in the Sandbox page at all.
Clicking Edit and then Preview on the original Sandbox page corrected the problem, of course.
Making the indexing only happen on a real commit might also speed the Preview up a small amount. --Chapman Flack