Heather here with a reminder/deeply heartfelt plea to leave an x-note in an item’s record when you’re marking it missing in Millennium! If you don’t leave an x-note that includes the date, it’s very difficult to exactly pinpoint when the item was marked missing, leading to all sorts of wild conjectures in the Technical Services office.
So, an item is missing from the shelf. You change the status to “m” (missing). Good, good. Now add an x-note, like so: “Item marked missing on 2/12/13 by HS.” Or something to that effect - the really important part is the date.