I don't think they would necessarily be dead. The DE goes through your intestine and the grains scrape them out and injure the worms. The DE probably put pressure on the worms to move out the back end.
Also that's why DE doesn't always work right away, because it injures the worms more and more every time you take it and kills them over time. That's some of the information I read about it on, at least. According to the testimonials and experiences I've read about it often works in a day.