My point about the post didn't come through. You asked if someone has never seen the Eiffel Tower whether it exists. Well, in a very real way, it doesn't. Not for that person. A person can only call into their mind abstractions of things they have already perceived in one form or another. It's actually a pretty fascinating function of the mind. Take one of oldfella's goats for example. If I say "goat" you can picture in your mind your version of a goat. If I say now picture a blue goat, you can because your mind can construct one for you from two totally different abstractions - the color blue and the previously perceived goat. Almost all imaginary things are simply just that - conglomerations of multiple abstractions that we have seen throughout the course of our life. Had you been born totally colorblind, you would not have been able to construct a blue goat. Blue would have no meaning to you. Blue would not exist at all.
Here's a test. I have a hand-painted icon on the mantle of my fireplace. Tell me what you think it looks like. Before you read the previous sentence, did that icon exist for you? No. Does it exist at all? Not an easy question to answer philosophically. I'll bet you can picture the fireplace and the mantle and you can probably even see the bricks (even though it's marble), but I bet you have no clue about that icon.
I think the root of these kinds of manifestations and tales lies right inside your post. In the beginning you say "trust me friend there is proof if you seek it long enough" but by the end you say "we just really dont know". Trust me, I'd like for there to be ghosts and spirits running around as much as anyone but I just can't put any effort into that brand of faith. It's hard enough for me to deal and struggle with the real realities of life that you mentioned - all the unexplainable things in life and the mystery and meaning of existence itself. Much more worthy pursuits. That's why I said what I said about keeping the fascination to a hobby level or just a mild amusement or curiosity and focus on reality.