I am tracking a custom Date field on the Account object because some of my records have mysteriously been updating. I've noticed that the field history takes note of my deleting of the value, but doesn't seem to audit the field getting set (which is what I am interested in). I've looked through the org and haven't been able to locate any custom code or workflow field updates that would update the field, so my question is whether there are any other ways a field could get updated and not audited.
UPDATE: It has happened again, and here is some intrigue to add. All of the accounts in the system were touched for an update this morning, and a new account has had the date switched from blank to a date. No activity history or chatter history update. Last modified date was from the "touch". Strangest part -- there is a validation rule on this field that says you can't give it a value unless a picklist is set to a certain value..and it is not.