It sounded like in the rulebook at the end that the "destroyed room" is now a blank space for the rest of the turn.
Check page 22 again. A 'Deactivated' room is treated as a "blank" space. A 'Destroyed' room is not.
Certainly it is clear that if the hero is in the room when it is destroyed, then the effect of the revealed room is null for that hero, but what about other heroes soon to pass through?
They will take damage from the newly revealed room when they enter it.