From my experience, comments do not show as part of the "version history" which means you can't use that to restore the previous comments made through the 'comments' feature. BUT here is a potential idea...did the comment include a "@mention" because if so, that @mention would have sent an email notification and in which case, maybe check in to see if that email notification (which comes in the form of an email) still exists so that you all can reference that to see what the comment said originally at least.