The best course of action in this scenario is for the project manager to seek interim funding approval from an authority within the project governance structure, such as the project director. This approach allows for the continuation of critical project activities without delay, which is essential given the expedited schedule of the project. Once interim approval is granted, the project manager should then bring this interim approval to the investment committee's attention at the next meeting for formal acknowledgment and inclusion in the project's funding records.
References: The answer is verified by the principles outlined in the PMBOKGuide, which emphasizes the importance of maintaining project continuity and the role of the project governance in facilitating necessary approvals for project progression. The PMBOKGuide also discusses the project manager's responsibility to communicate with stakeholders and manage project constraints, including schedule and funding. The Professional in Business Analysis (PMI-PBA) reference materials further support this approach by highlighting the need for effective stakeholder engagement and decision-making processes within project management practices.