How do I update a Infopath form, with SharePoint list data

I have a form that is used to initially submit the data to to the list. then I have a column which assigns a tracking # to that list item.

what the client wants is to have that tracking number to be in the InfoPath form.  the  tracking number is created via a workflow to update the list column.  but that column is not in the initial InfoPath form.

how can I add that tracking number to InfoPath form?