A similar incident happened to her 6 months ago, when she was hospitalized overnight for dehydration. She was sharp as a tack at the hospital, made eye contact with us and the doctors, and talked up a storm. This lasted for a few days after coming home, before reverting back to her baseline of having no short-term memory, being withdrawn and having a vacant stare. (We did keep her hydrated after returning home with her, so we didn't think that factored into the changes in cognition).
I tried to find an Article here on Aging Care about showtiming, but nothing came up in my search. Maybe other caregivers here can help you out.
I just recently learned there are certain genes in our bodies that are turned on by "heat shock". Which is why saunas help people live longer. Who knew? I think our bodies and brains are still largely mysterious, even to doctors. I would be the cold triggered some biological reaction that cleared mom's brain synapses for a short time.
We don't know enough about dementia to give exact answers and no two people will react the same at the same stage of dementia anyway.
My mom is in stage 6 Alzheimer's. She has no memory at all-recent or past. She isn't able to answer many questions, yet she remembers her sister, Lorraine. Why she can't remember the other 5 brothers and sisters, who knows?
Sometimes there is no explanation for how dementia works.
We've only been studying it a comparatively short time. People died much younger even 50-100 years ago. Our generation is really the first to deal with wide spread dementia. So we're learning as we go along.
I'm not sure the demented person could pull off several days of "show timing". I guess it depends on the degree of confusion.