Which scenario would require a security officer to write an incident report?

When a theft occurs on the premises, it is crucial for a security officer to document the incident through an incident report. This report serves multiple purposes, such as providing a detailed account of the event, documenting evidence, and establishing a record for any potential legal proceedings or investigations. It ensures that all relevant information, including the time, location, individuals involved, and the nature of the theft, is clearly captured and can be referred to later.

In contrast, the other scenarios listed—such as a fire alarm test, an employee's lunch break, and a routine patrol—do not involve emergencies or incidents that require formal documentation. These situations do not necessitate an incident report as they do not represent unusual occurrences or events that require follow-up actions or legal considerations.