I know you know this, but for others reading, GJ secrecy attaches to the jurors and the prosecutor, not to the witnesses.
Natrually, witnesses don't know for a fact that an indictment exists. That fact is known only to the jurors, prosecutor, and court. But some aspects of GJ proceedings are not bound up in secrecy by law.
Right thanks for the clarification. My post was only supposed to apply to an actual indictment, not all grand jury information. Presumably, the indictment would not be known to someone who was just a witness.