It's not my adblocker (it's turned off), and I haven't changed any settings. Did I do something or is the site having a moment?

There's a button on the menu bar that says "Toggle Sidebar". If you click it your sidebar should come back again. Its very easy to hit this button by accident, so you would not be alone in doing so!

Thank you! Never even noticed that before, how in the heck did I manage to hit it?!

You're not alone I've done this before and freaked out, haha.

If you don't want to worry about accidentally toggling it off again, you can use custom CSS to hide the button entirely.

Custom CSS page

-toggle-button {display: none;}