I believe I did see an increase in chest drops with multiple Potion of Treasure Finding, but I couldn't totally attribute the increase in drops to the extra potion. It wasn't that great of an increase. I was getting about 17-20 chests with 1 potion and maybe ~25 with 2 potions. It's possible that I just got some extra killing done or a better run against the RNG. After about 3 hours I decided it wasn't enough of an increase vs the cost and I was simply better off using the potions one at a time.

Like the cloth scavenging, I think the treasure chests were first come first serve, so I don't think my slave actually looted any.