I am chuckling as I read these posts and am tripping down memory lane...
There have been a few times when I could not round everyone up and put them into their housing early, when I needed to. I closed up the coop, put some hiding places (big barrels on their side, creating what I hoped was a safer space for them), and hoped for the best.
When I got home, it was dark, and I found the chickens in the hiding places I set up or on the deck railing. (The chickens have been taught to go to the deck if they need a "safe" place.)
I've had one cockerel who was just happier roosting on my "social chair." It didn't seem to matter where the chair was, THAT was where I would find him at dusk/dark. I would pick him up and move him into his house. I finally stopped and moved him to the deck. He was always happier sleeping outside, than inside. Now that COLDER and stormy/windy weather has arrived, I have moved him in with a flock. He still wants to sleep outside, but he's adjusting. (Today the high was 54.) All of my housing for the animals is considered to be very generous in size - crowding wasn't an issue. I clean the animal spaces daily - filth was not an issue. He was definitely a more dominant cockerel - so bullying wasn't an issue. He just prefers to sleep on the social chair.
Social chair - I have a folding lawn chair that I take with me when I visit with the animals. I set up the chair in different places.
A previous friend had a major issue with chickens nesting and roosting elsewhere. Her coop was TINY (think 50+ birds for a coop that was 3'x4' and that INCLUDED the nesting boxes along one wall) and FILTHY (think it was NEVER cleaned out in several years until I came along.) I cleaned out the coop a few times because it was so disgusting and SMELLY. Chickens would die around the coop and she wouldn't remove the bodies. When I would mention it to her, she would say she knew it had died.
So --- there may be a few reasons why the chicken isn't coming back that others mentioned (lost her way, being bullied, she feels it's too hot/crowded/whatever.) And it may be that the chicken has an independent streak.
The coop looked large enough for the girls.
Could you expand the run?