I had a snake do the same thing once. I might have been wrong but at the time I wondered if it had hurt it's jaw biting a rat. Anyway I sized down to smaller size. I think I even tried large mice for a while. It eventually went back to small rats.
I would do a large mouse to see what happens. If it don't swallow the mouse than I'd say it might not be hungry. But usually when a snake isn't hungry it avoids the meal or just smells it and goes away from it.
Or maybe this is just a weird type of winter fast and it wants to keep them squeezing muscles in shape.
Opps I missed where you said it ate last Thursday. Glad for that anyway.