there are these scientific phenomenon called **terminal lucidity or dementia clarity** which is actually happened in many cases which we had not yet researched fully. actually there are some cases where a grandmother with accute Alzheimer's recognised and talked to her granddaughter whom she was not recognising for years. unfortunately that grandmother died two weeks later.
[scientific paper](https://www.sciencedirect.com/science/article/pii/S1552526019300950)
[for more reading about terminal lucidity](https://www.griswoldhomecare.com/blog/2019/may/terminal-lucidity-dementia-clarity-before-death/)

Doubt it. Memory is dynamic on the neurons level. Each time you recall something you literally changed it because the neurons rebuilt connections structure all the time.

those are still still stored in there, but they lost the pointers to it. 