Sorry for your loss Matt!
I find there has been a lot of "moss trouble" with SE plants lately, due to poor mounding of the plants.
Plants used to be mounded with a hollow dome, or the smallest with a packing peanut underneath the plant, but the ones from this summer were in a big ball of very tight moss (not hollow), and I made the mistake of not checking them as soon a I received them (so used to SE plants quality).
Some very nice plants (not inexpensive! Akogare, Koganezuru, Shishinden, Keshomaru) ended up in emergency care with no root and I am not sure I will bring them back to life

Make sure to unmound when you receive the plants people ! Lesson learned...