Saying "we can't wait for help here, because if they've only explored to the third level, they might not be able to find us" seems a bit goofy.
If you stay there, there's literally a hole above your heads that goes all the way back. And it's not like it's singularly deep, it looks like it has individual floors the whole way up. So a rescue team with climbing rope could probably make their way down pretty quickly to help them.