Autosave is a safeguard in case you were to accidentally close the page you are working on, move to a new page or mistakenly walk away from your current session for a short while. The autosave only allows you to retrieve (notes, etc) within the same session so ending the session would result in losing your work. You must click the Save Note button to properly save.
Remember, you can review the History tab on the candidate's profile to see all the activity/action associated with that candidate. Activity, context, details will be noted and time stamped. This is where you can check to see if you had added and properly saved notes.