What happens if there is no proof of service for a subpoena?

The DA is attempting to have me testify against a friend of mine in a jury trial. The trial starts tomorrow morning. The DA called me earlier today, but I told her she had the wrong number, because I would really rather not testify. I got home this evening and found a subpoena in my door handle, however, there is no certificate of service. That portion of the form is left blank and not signed or dated by a server. FOR NOW, am I still in the clear? Don't they need to prove that I have been properly served?