Then I would say it is a bleached out Heteractis malu, or crispa. These are harder to keep than bta's and they live on the bottom with the base buried in the sand or at a sand/rock interface as some people have called it. I wouldn't recommend it for your first anemone. White is not a good sign. It may look pretty but it is a sign of poor health and if given a good environment it will color up and no longer be the white you wanted when you bought it.
I would read up on the different anemones, E. quadricolor, M. doreensis, Heteractis, sp., Stichodactyla sp. and learn the basics of what they look like and their environments and then go back to your lfs and ask them about the anemones (pretend like you don't know anything) and then specifically ask them about the anemone you saw and suggest it to be a Sebae (Heteractis sp.). From this conversation you should be able to determine how much the employees at the lfs now about anemones. If they can't provide much useful info I would suggest going to another fish store.
In my case I learn very quickly and in the short span of time I've been reading I currently know much more than the people at my lfs about anemones but they have a much better general knowledge about most sw fish/inverts, which I can easily say I don't know much past what I have experience with. I happen to be lucky to have a good lfs.