Happily Adobe are aware of the problem and have released a fix which you can read about here.
If, like me, your Creative Cloud app isn’t aware of the update yet then simply go to Photoshop’s help menu and click on Updates…
Recovering Your Lost Preferences
Of course the fix doesn’t help restore your lost Photoshop preferences so unless you have a backup of your preferences files or have used Photoshop’s “Sync Settings” feature then you’ll have to restore them manually 😦
Luckily I always keep a backup of my Photoshop files (see my previous post “Restoring Photoshop Settings” to discover how to do this) but I’ve never actually looked at how the “Sync Settings” feature actually works.