I have been battling my clowns for about a year now. They grab by red knobbys and carry them into the anemone.
Luckily, I work at home and their tank is close so I am often watching and catch them in the act. Several times, I have found my beloved Patrick sticking out of the mouth. I have pulled them out and they are covered in a slime coat and aren't moving. They usually remain stiff for a few hours then slowly start to revive.
While one of my knobbys is missing, the others are still kicking in spite of being pulled from the belly of the beast.