Did my Brittle Starfish eat my Anename?

[TICKLEmyTOTS]

I have a Caribbean Blunt-spine brittle starfish and think he just ate an anemone I introduced to my tank today. Unfortunately, the tentacles of the anemone were not out so he could sting the starfish. I watched the starfish pull him under the rock and disappear. Is this a thing? I thought these guys were reef safe? Did he really just eat my anemone? Is this a thing?