How to redisplay directories under the project sidebar.

I don't know what causes this. Maybe I'm hitting some keystroke or something but I constantly find the project sidebar on the left not showing my source code directories ( or any directories) for that matter. There's nothing special about these directories. This project I have a two directories of go code, one directory of testdata, a bin directory and a docs directory. Can't seem to have them displayed in the project browser anymore.

Usually re-opening the editor fixes it but not this time. If I have multiple projects open like I typically do, it only affects the one.