A single reference number across documents allows the search function to find the whole trail in one hit. One such field already exists the FOB field.
In my case I have a job number system which is entered in the FOB field which I call Job number on every document. (I have no other use for an FOB field)
When I search The FOB for a number it will find every invoice Purchase order, etc etc associated with that job number.
This is a huge time saver. Add the fact that every job goes into a folder with that job number and the whole job is then searchable with backwards cross references and it just happens by default.
Although it seems that I have the answer, now that I am trying to retire the manual job ticket and replace it with a sales order, I run into a snag. The logical answer was to have the SO number become the job number, but the only way to that and keep my referencing system working is to copy that same SO number into an FOB field.