No audit is guaranteed to uncover fraud, even if it is suspected. The most skilled auditors out there will never guarantee they'll find fraud even if it does actually exist. You can certainly tailor the audit to increase your likelihood of discovering fraud, but there is never a guarantee.
Some of the SEC auditors are not bad. The problem is Congress rides the SEC and hedge funds have been given a free pass. Way too much politics at the SEC.
Never a guarantee, but you can sure improve the discovery rate. And how many auditors have you heard of whose compensation packages would result in a huge windfall for them if they uncovered a huge fraud? There’s a huge amount of pressure on auditors to keep the client happy (in the case of outside auditors hired to produce audited financial statements), and on internal auditors not to rock the boat and to play along with internal politics (which are controlled by the senior executives whose units are producing the highest profits), and on regulatory auditors to follow procedures and follow orders from above. There is no category of auditors which is incentivized to uncover fraud beyond the level of scams operating out of a boiler room.