Back 2 Back Order Not Finding ASL Record

I'm trying to set up a simple back-2-back order process (i.e. supplier drop ship) and my supplier is not being found. I'd like the process to generate a standard purchase order when complete. It seems like it should be simple so I'm perplexed. (R12.1.3)

The item is a standard item (not configured). My sales order to the customer:

At this point I have a record in po_requisitions_interface_all - but that record has no suggested vendor on it. (Should it? or should a later step add this?)

My ASL:

My sourcing rule:

My assignment set:

At this point: