The reason you don't see the user details in Site Admin in this case is because when a project is restored into the Site it will only bring the user's login name with it, and only that will be added to the Site. Projects contain only the user login names. When they are restored/imported into a QC site that is the only information that is available to add to the Site for the user.
There are multiple methods for importing the full set of user data for a site. You could talk to your DBA about exporting the data from the v9.2 USERS table and importing it into the v11.0 USERS table.
You could look at writing a program that uses the Site Admin API to get the user data from the v9.2 system. Then write a separate program that uses the Site Admin API to add the data to the v11.0 system.
If you are using LDAP integration, you could manually re-import all the users from LDAP into the v11.0 system.
There are multiple methods for importing the full set of user data for a site. You could talk to your DBA about exporting the data from the v9.2 USERS table and importing it into the v11.0 USERS table.
You could look at writing a program that uses the Site Admin API to get the user data from the v9.2 system. Then write a separate program that uses the Site Admin API to add the data to the v11.0 system.
If you are using LDAP integration, you could manually re-import all the users from LDAP into the v11.0 system.