Stairs shouldn't be counted by the game's pathbuilding procedures, or else you stand a chance of having to go up a few floors in order to find the one set of stairs that you can use to get to that other set of stairs that you can use to get to that third set of stairs that you can use to get to where Dredmor is hiding. That's lame.
I have had that multiple times in that level configuration (with an artifact in the room above). I figured that you couldn't get them unless you had teleporting.
Well you could get in/out through numerous means (teleport, blink (self displace as well, but that's very difficult and unlikely), knockback on bars, digging) Blinks, knockback and digging are all available on items, and teleport is in three trees, blink in one (plus one in dodger if you count that), digging in two, knockback in four. That doesn't include the previous items some of which are easy enough with crafting tools.
I've had better then that actually.. a "mysterious realm" portal that placed me in a room with no doors, levers, gates, pasageways, bars, portals or ANY way of leaving the room... thank god that wasn't a permadeath game and I'd saved before entering the portal.
