Yeah, I'm a little confused myself. Ducker's page has the following note:
Where is this information from? I feel that this note needs a reference.
There is a single reference to it in the series:
"Although the labyrinth we went to had already been cleared, there were still unexplored areas within it. One of the members discovered a treasure chest when we were preparing to leave. I recommended leaving it alone, as we were close to the front lines so the monsters had high levels. Furthermore, I didn't trust the trap dismantling skills of the members. But since only Sachi and I opposed opening the treasure chest, we lost 3 to 2 on the vote."
So yes, it does exist, just that nobody noticed that it wasn't listed.
Edit: Lol, TUSF cut in front of me, but my reply is a suitable follow up to his post XD
Anyway, skill added to the list with a reference.