I think that's what happened:
game: #10624918
Turn 19 - blamelewis
b plays a Herbalist.
Herbalist is enchanted by Enchantress
b draws a Farmland.
b plays 3 Coppers and a Silver.
b buys and gains a Duchy.
b topdecks a Silver.
b draws a Silver, an Estate, a Smugglers, a Scrying Pool and a Farmland.
That's actually correct.
Enchantress changes what happens/is executed when a card is played. But the card is still played, it still goes into play and so still has all the "While this is in play" effects, that are usually below a horizontal deviding line.
So while Herbalist did not provide +1 Buy and +$1, it still has the ability to topdeck a treasure.
Fair enough... thanks for clarifying.
Best
Tim