exceptionally smart childen do have very explicit imaginations. My 3 yr old grand-son absorbs everything around him. He tells some good stories sometimes so you have to go through and figure out what is what. He is putting things together but not in the context that his new knowledge is meant for. Oh thats the med flight helicopter going south must have been an accident bet that big semi rolled over and smashed that truck hurting those people someone might be dead ok on the news he say a semi turned over noone hurt but later saw an accident that someone was hurt so his imagination put it together
oh that boy pushed that girl down so he doesnt like her no what happened was the little boy tripped and fell into the little girl that mom doesnt like her kids she is yelling at them yes she was at the playground to get their attention to go so watch this lady carefully but also see what is going on he maybe putting some things together that dont go together just because he has the knowledge to do so and an imagination to follow
Since you have already confronted "this person", I would give this "person" the benefit of the doubt. That does not mean your child is lying - it could be imagination or a dream that seemed real. That being said, I would still be very vigilant and keep my eyes and ears open whenever "this person" is in the same vicinity as your child. I can't see how noticeably "investigating the matter further" would make things better.