Why do my files keep disappearing from xcode's project navigator?

Question

The project I'm working on started as a single view application with storyboard, and I've added 2 more view controllers, each with a .m and a .h file. However, every time I save, quit, and then restart, the 4 new files disappear from the project navigator. I have to hit "add files to project" and drag them in manually from the project's folder each time. It's not terribly inconvenient, but it's annoying enough that I've basically just been leaving the project minimized whenever I'm not working on it. Does anyone know what's going on, or how I can force the files to remain in the navigator? This kind of thing has never happened before.

Answer 1

You probably are having a filter to show only recent files. To toggle that,

Answer 2

there is a button on the filter bar to "show only recent files"; the icon looks like a clock. You need to toggle this button to show all of your files.