IMO bigchops, if the cash has not come in through the door, they...

IMO bigchops, if the cash has not come in through the door, they could still issue NBS with an unqualified report provided NBS provide other suitable appropriate evidence that the monies will be received eventually. Some of the steps they could perform would be to:
1. Confirm the outstanding balance with the debtor directly
2. Vouch debtor make up to invoices (provides very low level of assurance)
3. Check subsequent cash receipts to confirm recoverability of debtor.

Given the materiality of the debtor, had PKF got any significant concerns about the debtor, they could have put in an emphasis of matter paragraph in the report to draw the reader's attention to the outstanding debtors. However no such modification was made to the audit report.