Final answer:
The most appropriate course of action is to complete an addendum to the patient care report and return to the hospital to add the important information.
Step-by-step explanation:
The most appropriate course of action in this situation would be to complete an addendum to the patient care report and return to the hospital to add the important information. This ensures that the patient's record is accurate and complete. Option C, completing an addendum and returning to the hospital, is the best choice in order to rectify the error.