Change purchase order draft line removes G/L account data

We created a purchase order and saved it as a draft.  We entered all information including G/L account and distribution rule but left delivery date blank.  When we go into the saved draft and input the delivery date, it removes the G/L account number.  There are many lines on this order and now we have to go back and input the G/L account number.

Any suggestions?

Thank you

Lori