Well, if it could happen, the "chilmato" would look like this
I am an American living in Yokohama Japan. Due to limited space I must garden in rather small containers, This year I have some jalapeños sandwiched between 2 tomato plants. The resulting peppers do not look like jalapeño, They are heart shaped. Could they have cross-pollinated with the tomatoes?
No, that's not possible, as the two plants cannot pollinate each other. The seeds or plants you bought were mislabeled or a hybrid.