Exactly. Or even- no known hallucinogens synthesized by their canonical biochemical pathways by enzymes expressed from the host species genome.
The OG hallucinogen, ergot, is ingested by eating wheat. If one presumed that the substance is made by wheat, and mined the wheat genome, they would never find the genes for its synthesis, because the hallucinogen is made by mold growing on the wheat.
It’s very rare you can draw a strong conclusion from negative results.

[–] boydster@sh.itjust.works 4 points 5 hours ago

Rye is the most common place ergot grows, which is another common bread grain. I am not disagreeing with your post, and ergot can grow on wheat too, just pointing out that rye is a much more common source of egot contamination.