If the LFS water was of poor quality then your acclimation time I would think should have been at least 2 to 3 hours. I have a brittle and a serpent (pretty much the same thing) and I acclimated them each for about 4 hours when I got them at different time and places. They both acted like they were dead. When I first put them in they seemd ok but after little while stopped moving and once in a while I would notice and arm move a bit. I left them alone for a few day and eventually they moved more and more. Now 6 months later they are doing fine. I hardly ever see the serpent but the brittle comes out to eat at feeding time and he has grown to twice the size of when I got him. He is about 12 inches from the tip of the arm to the tip of the opposite arm.
I would say just give it some time like 2 or 3 days and see what happens. You might also try spot feeding it if it starts moving. Stars are extremely sensitive to changes in water parameters which would include pH, temp, sg, ammon, nitrites, nitrates, alk and probably more.