Here is a thought: A being not visible to the folks in palace party central, Babylon (Daniel 5) physically wrote upon a wall with only the hand in our spacetime. That being I presume to be a messenger, an Angel. If an Angel can reach from their spacetime coordinate realm into ours then I presume they could mate with human females. ymmv
I see no reason to just assume the hand is an angel. If God can create mana, bread and fishes out nothing he can certainly create a disembodied hand, or the illusion of one. I don’t. think reading such preconceptions into scripture is proper hermeneutics.