I thought that the reason there weren't any unicorns was because they had all been driven into the sea (due to Noah forgetting them or an evil wizard, I never could decide which) and had become Narwhals, which are a type of whale with a sharp unicorn like horn on top of their head that I found in my National Geographic book of animals.
It was a strange fusion of ideas, but hey, the europeans were fooled by narwhal horns for years and counted them among religious artifacts.
A childhood belief about general

others believed things like this
- That unicorns were real. They simply had invisible horns that only people with special eyes could see
— Katie - I used to believe that unicorns were real creatures. I thought they were just another type of horse.Anon
- I used to believe that unicorns were real animals until I was about 16...lol...— Tara
- I used to believe that copying definitions out of a book counted as plagiarism!Anon
- I used to think the song "Who Built the ark? Noah. Noah." was "Who built the Ark? No one, no one!"— Embarrassed Kent Girl
- I used to think an evil spirit type thing called Wango lived in my dog. I was terrified of that dog.— Franklin