Ctrl+N seems to have deleted my scene

I was doing the Junior Programmer tutorial, the part where I create the Player Controller script for my custom game. I wanted to make a separate scene within the project to test some physics stuff, so I hit Ctrl+N, and clicked a new 3D scene. It seems to have totally overwritten the scene I was working on. All of my assets are there, but that doesn't include anything from the hierarchy. Hierarchy is totally empty except for camera and d-light.

I was making sure not to save while I was testing things, so I closed the project entirely and reopened it only to find the same thing.

1: What happened? 2: Can I get my scene back? 3: What is the purpose of Ctrl+N? seems like it's only there to erase the scene you are on. Is that right? Even when I do Ctrl+N and then Ctrl+Z, I can't undo it. Super mad about it. The tutorial had me make a backup, but it was only a backup of the Assets folder, which is exactly what I don't need, as the Assets folder was the only part that was unaffected. Send help!