In actual fact, they did find the cause of PharLap's death.
An Australian scientist who worked in conjunction with a museum expert managed to purchase a particle accelerator from the US. Using this device and a small sample of PharLap's mane from PharLap's museum exhibition, it was concluded he was induced with a large dose of arsenic around 35 hours before his death.
It is believed the work was carried out by American gansters, as they feared their illegal bookmarkers would lose.
You can see the full story here: Phar Lap death mystery solved | The Daily Telegraph