Look behind and under everything in your coop and run, in case it became trapped. Did the chickens come in on their own last evening, and did you have a head count? Do you see any feathers or blood? I hope you find your chicken.
Chicken wire is not predator proof. Raccoons can pull chickens through it, and weasels can slip through it.
Search house coop/run and yard. I would go out and call shaking feed in a cup in case found refuge somewhere. Leave no stone unturned. Check your perimeter for signs of attack. Best of Luck finding the little one!
I had a polish hen that was the lowest in pecking order, and I would find her squeezed into the tightest spaces hiding. There also was a tiny bantam that had scratched out a hole under my hospital crate where she was hiding eggs. Chickens can climb up on nest boxes and fall down behind them becoming trapped. Turned over buckets are another danger. It is always a good habit to do a head count at night, just to make sure everyone makes it inside to roost.
Earlier this month you posted you had a fox getting your chickens every night. Is this the same coop?
Did you ever figure out an fix whatever was wrong before?
I would really love to see some pictures of your coop or coops to get a better idea of what we are talking about.
Its very hard to tell you what it could be going on, with the information we have.
Maybe your pullet was taken during the day and never made it in the coop last night?
What kind of fensing? Run or free range?