There are a lot of things in the standard that don't require documents or records.
There was a time when auditors were actually trained (or seemed to be) that for every shall in the standard the auditee needed to produce a piece of paper (a document or record or sometimes even both). The standard NEVER required it.
Besides looking at documents and records, there are two more tools auditors have, and that is interviewing and observing. Even if there are documents and records to look at for a particular shall, they can still interview and observe (and often do).
An example on maintenance where an auditor could write a nonconformance even though maintenance records are not required would be if there are frequent breakdowns causing production delays and messing up delivery schedules or producing bad parts. The standard still requires that the infrastructure be determined, provided, and maintained.
By the way, if an organization chooses to keep maintenance records, they can be audited.