That's not true. The original people who saw it (with their spiritual senses) also claimed that others could know it was real (with their spiritual senses).
If the world didn't get to see it, or can't see the literal face of, or a pointy appendage of God, or can't see the difference between this religion and every other religion that makes claims based on one's subjective spiritual senses, then that's a problem for them (and their obvious spiritual deficiency).
Why does everyone leave out the important details??
With all due respect, this is an extremely theological version of the Emperor's New Clothes: conveniently non-falsifiable and if anyone points it out, they're a bad person.
If the world didn't get to see it, or can't see the literal face of, or a pointy appendage of God, or can't see the difference between this religion and every other religion that makes claims based on one's subjective spiritual senses, then that's a problem for them (and their obvious spiritual deficiency).
Why does everyone leave out the important details??