BooBoo...
Is this shop by any chance in Charlottesville? I've seen the flat mats in Pet Forum in Charlottesville and they look very similar to a sand anemone I have in a 10 gallon nano. It's only about half the size of the ones I've seen offered in pet forum however so I can't be 100% positive they are the same. Information about them is pretty scarce however. I can tell you that mine likes the light (tank has 6 watts per gallon), it moves around more than my other anemones, it accepts cut up fish, shrimp, clams, and photoplankton.
Also if you did see these in Pet Forum don't count on it being a flat mat or sand. Although pet forum is a great store I've purchased LTA, bubble tips, carpet, and "sebea" anemones all from a tank labeled flat mat and for flat mat prices. This was even after asking the store employee many times if they are sure they will sell it as a flat mat.