It can cause problems like anything that dies in your tank with a parameter spike. If you see it dead I would take it out. Most of the time the cuc takes care of business before we even notice it's dead.
Thanks Nick, I'll have my wife check it when she gets home from work. The clam was opening and the slit looked fine when I moved it so hopefully when the lights come on it will be ok. Most of the foot was attached to a piece of rock, but there was also a bit attached to a Turbo Snail shell. So hopefully it will make a comeback.