That was an exact condition a cousin's husband had to deal with as a union representative and Amtrak railroad engineer. He fought aggressively (and won) for any union member who was in such an unfortunate position.Suppose you had to administer drug tests where you work. There's a new employee you have known for years, with their whole future and their new family depending on the job. You know that they love poppy-seed muffins. You know that your testing machine can't distinguish between poppy seeds and heroin. Do you report their false positive as fact, as required in your job description?
Though he also recommended everyone refrain from eating anything with poppy seeds in their own best interest.