A childhood belief about swearing

When I was very little, about two or three, I was in a home day care. The lady who owned it had her kids help out a bit. Their son, Justin, who was twelve at the time was playing with me once and he was probably teaching me new words. He taught me the word ''truck'' except in the form of ''the F word''.
Well, one day when my parents were driving me home from day care, I saw a truck and started yelling the F word repeatedly, pointing to a truck. My parents were quite sure sneaky Justin had taught me that. He's done goofy things like that before, like putting pom poms in a certain place on a Halloween skeleton at seven.
We met him a few years ago. He was in his twenties. My dad told him this story and he was beet red!