You'd be surprised how fickle the human memory is. Sometimes you don't remember something important while reading a story because you didn't understand its significance until much later. Most readers don't remember the first time Wolverine was referred to as "Logan" because we didn't know it was a clue about his mysterious past.
Other times, we just remember the bare bones of a story. One of the most significant moments in DC Comics is when the Flash crossed over into another Earth, proving the existence of the multiverse. Although nearly every DC fan knows this, most of them can't tell you how the Flash stumbled upon this other universe. Stumbling upon another reality seems like the sort of thing you would remember!
Considering how convoluted comic book stories can be, you can't be expected to remember every facet. Even if it is a story that you love and have read many times, there are some parts that seem to slip past your memory. Maybe you were focusing on the revelation of a certain character or plot point to not notice something else.
With the benefit of hindsight though, it seems crazy that we forgot these bizarre moments in some of the most iconic storylines...
James Egan is on YouTube under Comic Kong with new videos every week. He has written 15 books about comics
1000 Facts about Superheroes Vol. 1-3
1000 Facts about Supervillains Vol. 1-3
1000 Facts about Comic Book Characters Vol. 1-3
1000 Facts about Comic Books Vol. 1-3
1000 Facts about Superhero Movies Vol. 1-3
Twitter - @jameswzegan85