Are you sure those are seedheads and not flowerheads. I don't see anything that looks like a pod to me. But then I'm not familar with the flower
you are trying to harvest.
Have you looked on the seed
site where they identify the pods and seeds
of different plants to see if they have a picture?
I know with the chives that I just finished harvesting I let them dry out completely then just held them by the stem and tapped them on the napkin and the seeds
fell out all over.
So if there were seeds
I would say they ended up in your luggage or they were never there. Or you just need to tap the seedheads on a paper towel or something that is mostly white so you can see them and see if they come out.