This same thing happened to me... I called the resident scheduled to be on-call on 07-01-07 and told him that he would be starting his call at 12:01am (luckily it is home call for him) and I notified the attendings on the service of the same. Everyone was cool about it.
You may want to consider NOT coming in on Saturday morning until there is a formal, written, plan in place for your relief at 12:01am. That should get their attention!! 🙂
Whatever happens keep the documentation.
Had it happen to me, too. I pointed out in no uncertain terms, months in advance that this was/would be an issue and the response from above was do it or else. I was in an extremely malignant program, run by not very nice people. I took exactly the approach that I was in the hospital as an observer, not a responder, this was documented in memoranda, that my contract and my residency had completed on 6/30 and my license ended 6/30. The fact is, if you do not have a license in those states that require them, you cannot participate in patient care. Even if nothing untoward happens, a crafty medmal atty will use that as a lever, make no mistake about it. "Tell me Doctor, what gave you the right to practice medicine on the morning my client died of ESRD when you knew you did not have a license?" No jury will hear this question because the hospital will settle the case and throw you to the wolves.
Or say, nothing at all happens, except some ancillary health care professional you've annoyed sees you writing orders at 7AM 7/1 and calls the licensing board and reports Dr. OP was writing orders in a patient's chart with an expired license, is that proper? Next comes the hearing, the reprimand, the fine and those pesky little questions. And let's not forget HIPAA. Are you allowed to know protected information if you are no longer a licensed professional?
I agree with LaDOC 100% on this. Kimberli, the chief is not competent, and this manifestation of this is the chief's/PD's responsibility alone. Outgoing residents happen every year. The chief/PD has through carelessness or worse, willful misconduct, placed the OP's future at risk, and placed the hospital at risk.
As you pointed out, this is no mystery. We all know this. Programs have been known to screw people they don't like, behave dishonestly and otherwise mess with people.