What if onsite the auditor and auditee realize the smelter is sourcing high-risk and needs to complete the high-risk assessment workbook?

First the auditor and auditee should talk through the changes.  If possible, the auditee can make the updates on site.  If not, the auditor may have to return to follow up.  This will also be reviewed in the context of continual improvement, understanding that new high-risk sources may take more time to address and integrated into systems and processes.