I used the anonymous WeChat trumpet to chat with a boy who has a crush on me for several days. Is it possible that he thought it was an acquaintance and guessed it was me?

More likely, you want him to guess who you are! You don't want him to guess, and he can't guess! If you just say you like him! He may wonder if his friends are playing tricks on him! If he has an object, he will think that the object is testing him! When you chat with him, his personality changes greatly, so he can't guess. Unless he knows that you like him, he may think of you! If he doesn't know that you like him, he can't guess! You have a great chance to chat with him casually with your own personality! He knows you well in advance!