And you can prove that...how?
Oh, more like an inference than proof. I don't know what would be called proof.
You use "church" to refer to a congregation and the building where they meet. But the definitions for "church" add up to a like minded group of religious people. The word "church" is just a sound that was assigned to that concept because people needed to refer to the reality. Grouping together, as in a church, is a natural human behavior. It just happens without anybody thinking about it.
People that are like minded on a certain point or points seek each other out and hang with one another. So Jesus would haven't "found" a church, as with the deliberate and willful act of "creating a church"; it would come about as a natural process of being human beings.
And I just assume that Jesus was understanding enough to know that process.