Sales Order Inquiry Zoom - Order Date is Blank

In MDGP 2010 when one

1. searches a Sales Document and goes to
2. Sales Transaction Inquiry Zoom and when clicks on Blue Arrow for DATE
3. the next screen pops up is
4. Sales Date Inquiry Zoom
5. Where Order Date is Blank, while
6. when you go to sales Order Entry Screen and click on the Blue Arrow
7. It shows the Order Date and later on Invoice Date.

Is there is reason for this field to be blank after posting or at some stage ?