Here are the basic rules for drawing cards:
If you discover a new room because of a tile’s or card’s
effect, and that new room has a symbol on it, you draw
the appropriate card for that new room. If a room is added
to the board through some other means (such as a haunt’s
instructions), the first player who enters that room does not
draw a card.
So in regards to Haunt 32 "Lost", the traitor is told to remove all tiles except the starting 3, the landings, and any player occupied spots. Then shuffle all of the discarded and newly picked up spots, to create a new draw pile.
Based on my interpretation of the rules, when exploring new rooms after the haunt begins, you would not be able to draw cards regardless if that room was used before the haunt. Is that correct?