I understand your anguish, believe me. EE's are my favorite, and I also have one particular one right now that I'm very partial to.
Before that, my favorite was Michelle a five-year old EE I had adopted after her owner died in a highway crash. One day a bobcat got into the pen and scattered the flock. After I'd located them, I knew one was missing since her pile of feathers were all that remained, but in my grief I couldn't remember who it was. When my mind settled down enough to think properly, it dawned on me that it was my favorite EE Michelle that had been killed.
So yes, I understand what you're going through. I sincerely hope she turns up, but sundown is a terrible period fraught with predator dangers. Perhaps, until your girls all begin to lay and get the hang of using the nest boxes, you might consider just confining them. Mid-day is a far safer period for chickens to free-range.
Please try not to beat yourself up over this. You wouldn't believe how dangerous my own "chicken learning curve" has been to my own flock.
