Final answer:
An unrecorded check issued during the last week of the year would most likely be discovered by the auditor when the cutoff bank statement is reconciled. This allows detection of checks issued but not yet presented to the bank.
Step-by-step explanation:
The question pertains to the discovery of an unrecorded check by an auditor in the context of financial auditing. When faced with identifying such an item, the most effective method would be through the reconciliation of the cutoff bank statement. This is because the cutoff bank statement will reflect all the checks that have been presented for payment through a certain period of time beyond the fiscal year-end. The auditor compares the company's records against the cutoff statement to identify any discrepancies, such as checks issued but not yet presented to the bank, which would include the unrecorded check in question.
The other options provided (reviewing the check register, bank confirmation, and searching for unrecorded liabilities) may not be as effective in this context. The check register may not contain the check if it was truly unrecorded, the bank confirmation focuses more on the balance as per the bank, and the search for unrecorded liabilities may not always capture unrecorded checks if they are not associated with a recognized liability at year-end.