I just created a List. Now I can't find it.
you can go to
Site settings > Under Site administration > click on the Site Libraries and Lists.
Or directly browse to this url( replace with site collection url)
This page will show all the List and libraries you created.
Click the Gear icon, click on Site Contents.
Here you can click the ... ellipsis and go to Settings then click Title, description and navigation and tell it to show on the quick launch (left nav).
I also see that the List shows up on as a New List App with the blue box around it under the Sites Contents page. I was used to looking for the List on the left Nav Bar.