How source organization is defaulted in Responsive Self Service Procurement

Hi,

when I add an item within responsive self service procurement I default to the master organization (which is the same as I have in the configure requisition business function) as the source organization. I have stock within another organization, should it default to the one I have stock on? How come it doesn't come? What logic does it follow? This does not allow me to add the item to the requisition.

Thanks,

Lorenzo