Domain search and readers field

Can anyone tell me why domain search and readers fields don’t work on one of my two servers?

We’ve setup domain search both on our Development server and a Staging server. On both servers, the document is secured because anonymous isn’t listed in the readers field.

However, on our staging server, the document title and summary is still showing in the search results.

The ACLs are identical on both db’s and so are the groups listed in the readers field. We use a single readers field to set hide/publish documents for the web by adding and removing the anonymous entry.