Alan,
Sorry to hear about your loss, especially when your heart is in the right place.
Don't know anything about anemones, but why can't two be kept in the same tank? How large was the tank they were in?
Don't know if this might have prevented the anemone from being sucked into the AC 300 intake, but I often cut a hole in an AC mini foam and pull it up over AC intakes to prevent accidents like the one you describe. Don't know if it would have helped in the case of your anemone, though, as it might have pulled off the foam anyway.