Each submission has its own activity feed which records any action taken on, or related to, a particular submission. All notes, reviews, messages, status changes, and edits are recorded in the Activity Feed with a time stamp.
You can download an offline version of the Activity Feed for any submission from within the Submission Details page. In the upper right hand corner, click More > Download Activity (.csv).
Questions? You can also contact support directly by filling out the form here.