Alma uses some Fulfillment vocabulary to mean very specific things:
Claimed Returned items were checked out by a patron and the patron claims they have returned the items.
Lost items were checked out by a patron and are either extremely overdue (and assumed lost) or were declared lost by the patron.
A Found item was marked Claimed Returned or Lost and has been found either by the patron or by staff.
Missing items were not checked out by a patron. They are supposed to be in place on the shelf and are not.
Items are only marked missing when they are missing from the shelves. Any item on loan to a patron may be marked Lost or Claimed Returned, as described above.
If you are pulling items to fill requests and one is missing from the shelf, use your local workflow to confirm and mark it missing. You might do this while processing the pull list; see the Processing the Pull/Pick List and Hold Shelves page in this guide for this process.