I don’t know what triggered this sudden change. I was in the middle of watching a YouTube video when suddenly the screen kind of logged out on its own and when I logged in I have lost the wallpaper (screen is black), panel, system tray, and application launcher. I have a shortcut to app launcher and it does not work anymore. Right clicking on the blank screen does nothing. I cannot reboot as I cannot access app launcher. Thankfully I have three virtual desktops open before the sudden log out with Firefox and Terminal opened. At the moment I cannot open any programs other than these two. One virtual desktop where no app were open is completely black. My system is up to date.
EDIT: I also tried
sudo reboot and to my surprise, my password is not recognized.