Lalato
Adventurer
I'm pretty sure this is the statue trap from KotS if you want to look it up in detail. Having DMed it, I remember it as a pretty lame/poorly designed trap - too easy/obvious to avoid the first part, too difficult to detect/avoid the second part. As I recall, pretty much without metagaming its impossible to avoid the 2nd half of the trap (though I am surprised it killed someone -I don't recall it being very difficult to dismantle/destroy it in time to save trapped characters).
Yes, this is, in fact, the trap. If the room was only described by the DM it might be difficult to know where to walk... but looking at the layout from above, it becomes kind of obvious. The second part of the trap would have been very easy to avoid with an Arcana or Knowledge check, but a skill check wasn't given.
So that's why I think it's using metagame knowledge for me as the player to automatically assume *trap* when I see the room layout... and have my character act accordingly. If the room had simply been described as having statues I might have thought there was a trap, but I wouldn't have necessarily walked the correct path.
I don't know if this is the most egregious example of using metagame knowledge, but it's one small example from the same encounter.