Since it is white, it has lost it's inner algae and cannot use Light at all.
You need to give it a chance to build its algae up and in the meantime it is trying to gain nutrients from the water during the night where the light cannot burn it's set skrive tissue.
The algae that gives it it's colour will also protect its inner sensitive tissue from the light.
Now it just wants lots of nutrients and a slow curve to get used to your light. Depending on its condition, it is said to take days to weeks for it to start getting stronger.
Feed it more regularly so it can give it's algae nutrients and it should bounce back.
It is impossible to remove an anemone from the wild without it fading alittle during the trip.
It's tissue is very sensitive and takes time to reshape to its new conditions, I would not try to move it back to the LFS now, as moving them is pretty hard on its structure to be honest.
Just give it time and attentive care and it should be fine.