Where have all my wifi credentials gone? My Oneplus One updated itself to the latest CyanogenMod kernel version a couple of days ago which has caused it to forget all my previously stored WPA keys and preferred wireless networks!

I was under the impression that all this information was cloud synced by Google, so why has it all disappeared now? Is there any way to force a pull of this information from the Android Device Manager, or do I just have to enter all this information (for hundreds of locations!) manually?

As of the update I'm running 5.1.1, Cyanogen version 12.1-YOG4PAS1N0. Kernel version is 3.4.67 and the build number is LMY48B.
This might be the case if the update had included an update for the Android WiFi driver, which might have caused incompatibilities with stored configuration data for networks. Try to retrieve this file (you will need to be root):

/data/misc/wifi/wpa_supplicant.conf

This file contains the configuration data for all WiFi networks which had been saved.

If this file is missing or blank, you will have to reconfigure the WiFi manually.