It’s not blasphemy to say good or bad things about an unapproved apparition, or anything else that you have no reason to think is something from God. The worst you could do is “saying embarrassingly badly judged things,” which is not a sin.
If you knew for a fact that something was from God, only then could it be blasphemy.
What the person said to you was a misquote of Rabbi Gamaliel’s comment in the Acts of the Apostles 5:33-40 –
When they had heard these things, they were cut to the heart, and they thought to put them to death. But one in the council rising up, a Pharisee named Gamaliel, a doctor of the law, respected by all the people, commanded the men to be put forth a little while.
And he said to them, "Ye men of Israel, take heed to yourselves what you intend to do, as touching these men.
"For before these days rose up Theodas, affirming himself to be somebody, to whom a number of men, about four hundred, joined themselves: who was slain; and all that believed him were scattered, and brought to nothing. After this man, rose up Judas of Galilee, in the days of the enrolling, and drew away the people after him: he also perished; and all, even as many as consented to him, were dispersed.
And now, therefore, I say to you, refrain from these men, and let them alone; for if this council or this work be of men, it will come to nought; but if it be of God, you cannot overthrow it, lest perhaps you be found even to fight against God."
And they consented to him. And calling in the apostles, after they had scourged them, they charged them that they should not speak at all in the name of Jesus; and they dismissed them.
I’m pretty sure you weren’t trying to get anybody put to death, so it doesn’t really apply.
Gamaliel didn’t say, “And seeing as how us Jews never ever argue out and develop religious matters, and neither do Christians, obviously we don’t have anything at all to talk about here in the Sanhedrin, so let’s just go home and skip the whole representative democracy thing!”
The bishops who figured out what books should be in the Bible didn’t say, “And don’t let me hear you argue one thing against 7th Enoch, because if we all keep our mouths shut, God will just send us a bulletin by angel mail, telling us what books are inspired!”
Part of how God expresses His will is by letting us argue things out, and gradually see what He wants us to do.
I will also say that the Apostles didn’t have much patience with crazy heretical stuff. St. John refused to be in the same building with one guy, because John figured he didn’t want to be there if God decided to smite him.