Credit Note posted without cost

Hi, 

One of my users have posted credit notes by entering negative values in the sales orders and not selected the return lot id, and effectively the cost of the item has not been affected for the selected warehouse but the inventory quantity has been affected and hence the on hand cost of each item is reduced, is there any way I can update the cost of the items now?

And if the user continues to post the credit notes in the future in a similar fashion, is there any way by which I setup AX to pick up the current cost price for the item?

Thanks & regards,

Ananta