No matter how prepared/experienced we are, there is always that surge of adrenaline when we are involved in an emergency situation. This is very different from 'panic'.
If that (calling 911) is the policy for your organization, you did the right thing. I'll bet you also initiated other actions - quick assessment, protecting airway, checking VS & LOC, didn't you? But, as an LPN, you should also have an RN supervisor that you need to notify whenever you encounter a situation that is beyond your scope of practice. It would probably be a good idea to clarify those expectations in order to be better prepared in the future.