Some nems aren't in great condition, and if the sebae you're talking about is a H. crispa, they're horrible shippers, and many (not all) don't make it. IMO, if it's near death it's not worth full price, unless there's some sort of guarantee for store credit or refund.
Please read through the clown/anemone FAQ's near the top of the forum, there's some really good info there about the different nems you may come across, their difficulty level (they all start at the difficult level and go up from there) and general care instructions. This may help you decide which anemone, if any, is right for you.
H. crispa and M. doreensis (two that commonly get labeled sebae) are both naturally sand dwelling nems, but in aquariums the rules of nature don't always carry over, and it's possible to find these above the sand on the glass or attached to rocks
(mine's attached to a rock with its foot just touching the sand).
FYI - I'm guessing you're fairly new (registration date and signature) - but I could be wrong, but just in case I'm not, most people recommend letting your tank mature for at least 6 months from the time the cycle ended before adding an anemone.
Good luck and keep asking questions, it's a great way to learn!
That's one thing you don't have to worry about 
