Requisition is lost following PO Cancellation

Summary

Created PO has been cancelled prior to final approval - requisition is NOT in Process Requisitions pool.

Content

We have recently upgraded our environment to Oracle Fusion R13 (from R12).

I manage a group of buyers who document build requisitions and submit for approval. 

Previously (in R12 and R11), if a submitted PO was rejected back to the buyer asking for further justification - the buyer would 'Cancel' the purchase order which would in turn return the requisition back in to the pool of requisitions in 'Process Requistions'. The buyer would then 'Return' the requisition asking the preparer to attach required justification and re-submit for approval - thus starting the process again.