Google Contacts, the address book built into Gmail, lets you keep track of all your contacts, see when you last interacted with them, and more.
Call out a changed proof before you confirm the creative decision.
Keep reviewers aware of changes to a proof before they act on a decision. Your task shows the mismatch and asks for confirmation.
Keep creative signoffs tied to their exact proof uploads.
Keep a clear history of who approved or rejected each campaign proof, even when the review board status changes later.