Active Directory Users and Historical Reconciliations

I am implementing ARM for a client and we noticed that when an Active Directory user is deleted, ARM shows "User ID is not found" for that user.  The client then raised what I believe is a valid question, what happens to historical reconciliations (i.e. locked periods) in that same scenario?  Say I close Jan 2015 period with Bob as Reviewer, the history show's that Bob approved the recons.  The period is closed and locked.  In Feb 2015, Bob leaves the company and his AD account is deleted.  ARM then will show that "User ID is not found" approved the