Cancelled Backorders

One of my business units has put sales orders on hold based on availability of inventory.  The inventory allocated on stock orders against these sales orders was on backorder on the 10th.  Fulfillment Status: Unfulfilled, Reservation Status: Pending Reservation.

They ran a query for backorders today, and the orders previously on backorder are now gone.  The Fulfillment Status is now Cancelled.  They insist they did nothing to cause the cancellation of these inventory items on the stock requests. 

Does anyone know how these back orders could be cancelled without any intervention?  I don't see any where a date or rule or other configuration that would cause this.  This has happened twice now for this business unit.  They are more into putting orders on hold than other business units using Sales Orders.  Not sure if that makes a difference.