YEs, the LFS was wrong, and the star was in trouble then and there.
Blue Linckia, FWIW are some of the most delicate animals we try and keep and most are doomed before purchase. They require a tank in excess of 150g with 200+lbs of LR minimum. Ideally the tank would be a year old with pristine water parameters.
They require very long acclimation times.
I strongly discourage their purchase. Many seastars in this hobby have similar requirements.
The only hope for it is to have it in a tank with ideal parameters, especially specific gravity, at 1.025-1.026.