China exports tons of frozen earthworms annually. Frozen earthworms are available in Europe as a fish food and fishing bait.
I wouldn't think the expense to freeze-dry earthworms would yield a viable product. Earthworms are larger than other available FD foods and would require additional dry ice and air time. However, earthworms are being dried (in those Ronco food-drying type machines) just like fruits and veggies. The cost is low and the shelf-life can be a couple of years with seal-a-meal bags.
They must freeze them quick, I tried to freeze some in a home freezer and they thawed out nasty.
I have never been a fan of freeze dried foods but that is just personal prejudice.
If they were deep froze it would probably just make them nasty anyways. I KNOW that worms can dry out though. You see them on the warm dry pavement in the summer after the rain in the thousands.