Speak with the attorney who subpoenaed you after getting a doctor's note. If the lawyer will not let you out, send a letter to the Judge and all lawyers involved enclosing the doctor's not which states the reason you cannot be in Court. Ask the Court to let you know what it decides in a nice way.
The information provided is for general informational purposes only and is not intended to be legal advice. I am only licensed in the Commonwealth of Pennsylvania and I am not providing you with specific legal advice. The law changes frequently and varies from jurisdiction to jurisdiction. Being general in nature, the information provided may not apply to any specific factual and/or legal set of circumstances and/or the jurisdiction where you reside. No attorney-client relationship is formed nor should any such relationship be implied. The information provided is of a general nature is not intended to substitute for the advice of an attorney, especially an attorney licensed in your jurisdiction. Your question, although you may believe is simple, it is not simple. You require legal advice, please consult with a competent attorney licensed to practice in your jurisdiction.
Are you a witness or a party? Civil or Criminal?
If a party, get a lawyer and have them file a motion for continuance. If a witness, send a letter to the judge and the lawyers explaining you cannot be there because you are scheduled for surgery. (I don't think I would tell them where.)
To answer your question, the original order covers recessed dates if the court ordered you to come back, which probably was done. You should talk to a lawyer for legal advice as to what to do. There are too many possibilities to get advice here.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.