Deleting rectangle when on base layer
I am following the Learnit Training Photoshop Full Course Tutorial on YouTube. At about 1:43 in, the instructor deletes a smart object rectangle on the base layer, drawn with the Rectangle Tool (keyboard shortcut U), by appearing to do no more than selecting it with the Move Tool (keyboard shortcut V) and hitting Delete. After he does that, I can see his base layer returns to just being a transparent layer (the layer created when creating a new document). I am using Photoshop on Mac and cannot delete my rectangle. I ended up deleting the document and starting over. .That video is now about 3 years old. Has the app changed? What am I missing? In future, should I lock my base layer and keep it transparent and draw everything in new layers on top so I can just delete the layer to get rid of the object? Thank you.
