reference information tab in AR credit memo invoice is returned null

1- i created a return sales order with reference type sales order2- when run auto invoice master program to create a credit memo for this return , the reference number is not populated 
in the reference tab i will upload Explain_Issue.docx.

scenario

1- create sales order no 775
2- create return sales order no 114 as in sales_return.docx.
8- run autoinvoice.
9- invoice created and credit created and credit not relate invoice as in invoice_return.docx

the main issue is when create return sales order in om and run autoinvoice the return sales order become 
a credit memo but i can't see any data in reference information tab.