Without wishing to argue the point, not a chance. The auditor has two jobs. First, to make sure that, in their opinion, the accounts give a true and fair view. Second, to cover their arses so they don't get sued to kingdom come if their opinion turns out to be wrong. Not necessarily in that order.
As soon as the leaks came out, they would have been on the phone. And the very next audit would have been strengthened to make sure that, in their, opinion, notwithstanding the allegations, the accounts gave a true and fair view. They would absolutely have looked at the sourcing of the funds to pay the sponsorship, even if it was just accepting a specific and detailed confirmation from the management/board/owner. Clearly, in their view, whatever they did gave them enough comfort to continue giving unqualified audit reports. If they weren't satisfied, they would have qualified the accounts or, more likely, resigned as auditors.
Trust me on this one.