Validity of a gift given with the owner's consent

I have a question regarding a matter of giving on behalf of someone….it’s kind off detailed…

Few years ago, my uncle took the responsibility of dealing with my grandfathers financial matters - with my grandfathers approval. At that time my grandfather was 100% mentally well but physically he was disabled and needed to live with someone to look after him. My mother (my grandfathers daughter) took that responsibility.

My uncle gave my father my grandfathers car as a gift (gift or kindoff payment for looking after my grandfather). Was this gifting valid?

Now my grandfather has dementia and isn’t in a state to make decisions, so it’s not possible to ask his approval of this gift. My father has passed away since then, so will the car be part of my father’s estate or is it still belonging to my grandfather?