Sometimes Windows get confused between when to enable/disable Tablet mode
Perhaps, when Windows 10 is fully released issues like this will no longer occur. But personally, I’ve encountered this a number of times, where for no obvious reasons it would switch to Tablet mode on a dedicated Desktop machine. At first, I wasn’t sure what to do, since the Start menu is the only thing showing on the entire screen. Unable to access my Desktop and all the Taskbar’s icon are missing. It puts me into panic mode where I thought my Windows 10 is frozen in a weird state, without investigating further I often restart my machine.
What really happened is the Tablet mode has switched on for no apparent reason. Why it was toggled on I’m still puzzling, but you can ensure this doesn’t occur in the future by going to Settings > Tablet Mode. Ensure that it always take you to the desktop and when to switch modes, ensure to prompt for confirmation. You can disable “Hide app icons on the Taskbar when in Tablet Mode” so you can still access the applications you’ve pinned to the Taskbar.