Lanefan
Victoria Rules
True, and also easily usurped by a well-spelled MU (Knock, Spider Climb, Fly, Wizard Eye) and-or Cleric (Find Traps) and-or a couple of handy magic devices (Wand of Secret Door Detection, Chime of Opening, almost any scrying device).And, frankly, the thief needed those significant moments. On so many other levels, the AD&D thief was a weak class.
Often the best thing a Thief (or Assassin) had going for it was if the DM allowed it to use poison on a regular basis.