Hello,
Undetected files should be submitted to Symantec Security Response for examination, after the computer upon which they are found has been isolated. Some good articles:
Best Practices for Troubleshooting Viruses on a Network
http://www.symantec.com/docs/TECH122466
Scanning a file with a competitor's antivirus program detects a virus, but scanning with Symantec Endpoint Protection does not
http://www.symantec.com/docs/TECH98929
How to Use the Web Submission Process to Submit Suspicious Files
http://www.symantec.com/docs/TECH102419
It is not recommended to run more than one AV scanner at a time. If more than one program is attempting to access, scan, and perform actions on a file, then malfunctions can result.
Should you run more than one antivirus program at the same time?
http://www.symantec.com/docs/TECH104806
Here's an article that will help getting samples to the team which can process them:
Symantec Insider Tip: Successful Submissions!
https://www-secure.symantec.com/connect/articles/symantec-insider-tip-successful-submissions
Regards,