My first instinct is to say its a ricordea. But... Like Traveller7 said, there have bee a lot of micro carpets showing up, in purple, blue and teal. There is someone out there that has perfected forced splits to the nano level on carpets. But I've never seen any that small so far.
Can you try to feed it a small mysid shrimp? Tell us if it actually opens it's orafice to eat it, or if it refuses and does nothing. If it is an anemone, it'll expand it's orafice to chug it down, otherwise it's probably a Corallimorph.