I guess one way, it would be unethical but bear with me, is to wait until there is a very important, must-win scenario for Hans. Then, you have him think he's playing his opponent, but really he's playing Stockfish 15.
If he draws, he's cheating.
I know it's unethical, but what I'm saying is it's not impossible to catch someone cheating. Another idea I had is to telegraph different moves from a game, to a live broadcast. Imagine they just show their faces and then a 2d diagram of the board. Then you see what happens to his play. This only works assuming he's not using an implant or a thumper in his shoe.
