Was it a Summons to Answer Interrogatories?
If so, you should go to court and tell the Judge the truth. That you had no knowledge of the previous court date (due to the move) but are willing to cooperate and answer the Creditor's questions.
If you don't appear at the Show Cause hearing, they might issue a warrant for your arrest.
You were not properly served, so technically you did not have to appear. However, that does not mean that a capias (civil arrest warrant) will not be issued if they think you were (although usually rules to show cause have to be personally served before that will happen). Better to appear and explain - you won't go to jail, you will just have to answer the questions or whatever it is that you were supposed to be there for.