You have to also remember that he has a lot on magic power so he could have used his magic to amp up the magnet in his wallet to a level were it could be used like this
So uh why is this listed as an isekai when the MC did not go over to another world, he just reincarnated back into his own world and like isn't the main thing about isekai is that someone is transported/reincarnated from one world to another?