In my org, I have a custom object whose Name field is an auto-number field and has another field which is a lookup to contact object. In the contact object I have a lookup relationship to this custom object. Since the name field is an auto-number field, the secondary field should be searchable in instant results as per this document (https://help.salesforce.com/articleView?id=search_lookup_config_lex.htm&type=5). In the search layout of the custom object, I have configured it as the contact field as the secondary field. 


As you can see in the above screenshot, the secondary field in the search layout is the lookup to contact. So as per the Salesforce documentation, I should be able to search the custom object records with the contact names in instant results. But instead, I am not getting any results. Is there any other configuration I am missing? Could someone guide me please?