Disco Stu is right.
The Schedule of assets held for investment actually requires two lists: a) all investment assets held at year end, and b) assets bought and sold during the plan year. The second schedule (bought and sold) has numerous exceptions, including most SEC-registered securities, bank CDs, government securities, etc. Also, any assets that are required to be reported on one of the other required schedules, such as the 5% transactions, or the prohibited transactions schedules, do not have to be reported on the bought and sold schedule. Most investments of most plans should be exempt from reporting on the second category. However, it is important to note that none of these exceptions apply to the first part, the assets actually held at year end.
Most of the time, I would expect the auditors to provide these schedules, because their audit report is required to address these schedules.