Hello,
There is no way to check from SEPM, specifically if the Cancelled scan was a "Scheduled scan" or a "User Manual Scan".
However, you chan check the same from Local Machine.
Could you check latest logs on the local SEP client machine -
C:\ProgramData\Symantec\Symantec Endpoint Protection\12.1.3001.165.105\Data\Logs\AV
OR
Check the Scan Logs from the client machine-
1) Open the SEP client GUI
2) Click on View Logs
3) Click on View Logs next to Virus and Spyware Protection.
4) Click on Scan Logs.
When scan is started the files are scanned, if machines are turned off or scan is interrupted during a scan.
The registry keys are set for missed event so that this scan be carried out once machines are back. However sometimes the interface gets stuck with current status and never gets updated like Cancelled, Paused etc.
If scan was running as per the interface then you cannot run another scan, it would say, it's queued as current a scan is active.
Scan status on SEPM monitor show as scanning, while action has completed in SEP client
http://www.symantec.com/docs/TECH199914
Interpreting the log files for Symantec AntiVirus Corporate Edition and Symantec Endpoint Protection
http://www.symantec.com/docs/TECH100099
Hope that helps!!!