Pet commands won't work. Just being on the hate list doesn't apply TH.
BGwiki said:
Treasure Hunter works as a debuff effect on the mob; the player with Treasure Hunter must take some aggressive action against the mob in order to apply the Treasure Hunter effect, after which the effect will remain even if the player is not in the party that kills the mob
ffxiclopedia also says something similar to this, but then there is also out-dated info about Treasure Hunter on there also; like TH wears off when you're wiped from the hate list. (Which it doesn't; TH remains until the monster is passive and regenerates (on a somewhat similar timer to how long it takes for Call of Help status to wear off a monster; unless the idle monster regenerates to 100%))
An aggressive action against a monster can be a pet command (like Predator Claws etc.)