When using a service containing just one layer, or when using a hosted feature service referencing a single layer, the Find Location By Layer option is available even if 'Search By Layer' is not configured in the associated web map.
This issue is expected behavior. Even if a web map does not have a specific feature layer search source configured within it, creators of the application may still be able to set up the feature layer search sources from within the app configuration panel if desired. In the application, however, the feature layer search sources are disabled by default, leaving it up to creators of the application to decide if they want to enable and configure the feature layer search sources or not.