CASE: You are completing the audit of Mann Pty Ltd. You read a note in the file from your assistant, Robert Jones, which states,

As required under the audit program, I performed a debtors confirmation to test the existence assertion for accounts receivable. However, there were three non-responses to the confirmation. Consequently, I sought alternative evidence for these. For two of them, I was able to substantiate the debt by reviewing subsequent payments. However, the third debtor had not paid, so I sought evidence that the debt had been incurred by reviewing the supporting documentation (duplicate sales invoice, and the corresponding shipping note and sales order).

REQUIRED: Has Robert satisfactorily dealt with the three non-responses? Give the reason for your answer.