With my old eyes, I could see nothing, but with my glasses, I saw the source of the bumps. Can you see them? You might have to click on the picture to see it larger, as I know you are now as interested in this mystery as I am.
While I'm great at putting things in my pocket, somewhat like a four year old boy, I'm not nearly as good at getting everything out. I believe those are basil seeds, seeds that must have spun out over the whole dress. If that isn't it, I have no other ideas. It was entertaining to say the least. I likely wouldn't have been as excited if all those seeds had sprouted.