I need to run a script on Vendor Bills, but only one ones brought in from Nexonia, which uses Web Services.  I am trying to create a condition based on Source, but the Source comes across as null. However, when I add the Source field to my List View in the UI, I can see a value of "Web Services".  The Source field doesn't seem to have a value when accessed through script or Workflow.  Is there a different, hidden field for the stored Source?

this is my criteria in the UE script, which runs on AfterSubmit:

var source = newRec.getFieldValue("source");