Assuming the list existed at the time it should have been included in the last days backup... Restoring a backup will cause you to lose all recent changes to everything throughout the program. This includes settings, new users, etc. Since the backup is actually a compressed SQL text file what you could have done is extracted the particular line(s) you needed and ran the queries with a custom MySQL tool such as PhpMyAdmin.
Regretfully if the list is not contained in the backup file you have to restore, and you don't have an 'Export' of all the users on that list so you might re-Import them you may have lost your data. If this is extremely damaging you might try asking your web host if they have any backups that they can restore. (keeping your latest one on hand for updating later when you recover the important data)
Regards