My earliest memory was from pre-school, when I was roughly around the age of 4. I remember going to school one day, and then going home telling my mom about this girl from school who had her fingers cut off with scissors.
So it turned out the girl was actually born without fingers on one of her hands, but back then, it didn't occur to me that something like that could happen. So it only made sense that her fingers got cut off, and the only way which I knew that something could be cut off, is with a pair scissors, so I came up with that 'theory' that I told my mom about.
Obviously looking back now, my 'scissors' story doesn't make much sense, and I probably wouldn't come up with the same 'theory' if I experienced the same thing now, but amazingly, despite this 'story' the girl and I ended up becoming pretty close friends. We went to the same highschool and still keep in contact till now, and ths erm 'story' does come up time and again when we meet up.
I can definitely identify with your reasoning in this memory. I remember having a similar experience whenever I was in kindergarden. I went to an all girls school and on the first day of school there was a girl wearing a dress but she had short hair and I distinctly remember thinking "oh i didnt know they let boys in, I thought it was an all girls school."
I guess, judging from this memory, you and I are both nieve at times and as a result come to incorrect conclusions.