Like wasp says, it looks bleached. If that's the case then it probably was kept in a tank with too low of light. So throwing it in your tank with, I assume, a lot brighter light would shock it and it's just trying to get away from the painfully bright light.
Anemones seem to survive ok while bleached as long as you feed them. Mine's been bleached for about 2 years and has about tripled in size.