Fortigate went down - Rotated logs access

Hello,

New Fortigate user here. Our Fortigate 101E stopped passing traffic during the night. The boss called me and after trying to access the web interface (unsuccessful) , we powered the device off and on. It's now passing traffic. I've opened a ticket and it was escalated to do a root cause analysis.

My question is this. Is it possible to view rotated logs? When the device was power cycled, the log files had rotated. I'm only seeing logs since it was restarted. If it's possible, how do I view the previous logs?

The device is running FortiOS 5.6

Thanks for any info,

Rod