PDF of letter from Tesla to DOT: http://www-odi.nhtsa.dot.gov/acms/cs/jaxrs/download/doc/UCM4...
PDF of response letter to Tesla: http://www-odi.nhtsa.dot.gov/acms/cs/jaxrs/download/doc/UCM4...
Fundamentally, it seems like a safety issue that has to be addressed is just called a "recall", regardless of whether the car has to be taken in or not. That's why Musk said no cars were "physically recalled."