FortiGate 90D: No Disk Available

We are having troubles with one of our FG90D's. It was blocking the internet and we had to reboot using CLI. Afterwards, we had no logging disk anymore? 

Running Diagnose on the disk says there is a disk mounted, but GUI doesnt see it. Also execute formatlogdisk says no disk.

FW10022 # diagnose hardware deviceinfo disk

Disk USB-2(boot) ref: 1.9GB type: USB [FORTINET 61_V030910_002] dev: /dev/sda partition ref: 251.0MB, 223.0MB free mounted: N label: dev: /dev/sda1(boot) partition ref: 247.0MB, 215.0MB free mounted: Y label: dev: /dev/sda2(boot) partition ref: 3 1.3GB, 1.3GB free mounted: Y label: dev: /dev/sda3

FW10022 #

execute disk list returns nothing but a new empty cli line...