Hi,
Was archiving configured? I have NCM configured to retain the latest 10 copies of every config file from every device, and it then purges old configs (any over 10) from the DB. I also have NCM configured to archive a copy of every single config file into a secondary flat file system/disk on the server. This file system only cleans itself up when I delete them manually.
Do you know if this feature is configured? If so, just access that file system location for your configs. This is the easiest method. That said, you can also go to the Configs tab - Configuration Management - locate/select the device(s) you wish to keep - "Download" the config files that are in the DB.
D