have you confgured the below before viewing the records
1: log in to Symantec Endpoint Protection Manager Console /SEPM
2: click "Policies"-->click " Application and Device Control" under "View Policies"-->edit or create a new application policy-->click "Application Control" -->on the right panel , enable " Log Files written to USB drivers"
3: click edit button to edit "Log Files written to USB drives" policy configuration
4: click "Log written to USB drives" under "Log written to USB drives" on the left panel
5: under "Properties" tag ,choose which USB device will be used for this policy, default is " *" which is mean all USB device will be applied with this settings.
6: under " Actions" , if you want to just record the creating, deleting or writing attempts of USB device, please click "enable logging" under "create, delete or write attempt". if you want to record reading attemp either, you need tick "ebable logging" under " read attempt"
7: click "OK" twice and then left click this policy and assign this policy to groups