How do you know those sins were forgiven? Did you get a receipt?
For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. For God did not send His Son into the world to condemn the world, but that the world through Him might be saved. He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God.Peace,
(John 3:16-18)
Before you ask myself questions, expecting me to answer those, it's only fair to say to you that you are running quite a backlog of needing answer questions which I have put to you.
Besides, the answer to the question which you just posed, was given some amount of explanation, already. I do not believe that any further answer would suit you, if it not fit within your own preconceptions.
Those who have been baptized in the Spirit (not merely only the water) could possibly understand, though.
When you return to the question (about John the Baptist) Christ posed to the Pharisees who were questioning his own authority (to preach), then that could be accepted as near to full payment to myself towards your own backlog of questions posed to you, but thus far have been left entirely unanswered.
But your question does bring to mind yet another set, too.
Will you need show printed(?) receipts to Christ in order to secure entry into His everlasting kingdom? Perhaps wave those receipts around in the air, when or if some dark spirits attempt to (as they attempted to do to Moses) drag your body off to some place? Would doing so ward off those demons?
The same question can be asked of Catholics.
How do YOU know?