For one thing, because it obviously happened long ago and you're not around 2,000 years old.
So...you do "believe" (meaning that statement is merely what you "believe") that such a thing is impossible for God, and you deny that the scriptures give evidence that He can. Thanks for making yourself clear.
Also, if you read the text carefully, you can see that Paul hints very strongly at himself being the one who was caught up to the third heaven, but he didn't want to say it explicitly because of not wanting to come across like he was boasting about it.
"Read...hints...he didn't want to say?" Speculation. Conjecture. Opinion. What you believe. That is merely your interpretation: Fail.
But let me help you out here--Yes, God
can do "long ago" when and wherever with whomever He wants to. But you are also wrong about prophecy, or who things might be referring to in one context as opposed to, or in addition to, another time, person, or context. Just take David's Psalms of his own suffering that are biblically claimed by the apostles to have been about Christ--correct in not one, but two different contexts...or of David's son building a house for the Lord God by Solomon, but also being more importantly true of Jesus--two again, and the One greater than the other...or of Paul who plucked the phrase "
by the mouth of two or three" out of the Law (out of context) to show his own authority among the Corinthians. The point being--you are setting limits that the scriptures show to be unfounded, even anti-Christ. Stop doing that!
Which means: No--you do not know what you think you know, for certain.