Retroactively posted entries not indexed in search?

I am noticing that posts I add to the blog retroactively (editing timestamp before publishing) are not showing up in search queries. For example, I have a post titled Sprout Man Will and the Liquid Aminos, retroactively posted with timestamp of 5/20/2005. As you can see from the link, the post is definitely in the database – but if you enter the term “sprout” in the search box in the upper right hand corner, you will get no results.

This is maddening, because I’ve put all these old entries in, one by one, and I can’t find them when I want to refer to them. Sure, I can go to Google and search my own domain, but that’s kind of a pain in the butt… I want my own WordPress search function to be able to find all my posts!

The reason, incidentally, that I’m retroactively posting stuff is that, for years I maintained blogs and journals on various platforms, and I want to get everything into one integrated place for once, so I’ve been steadily posting old items as I stumble across them in my files.