How was Retribution stolen?

[Antonio]

Can anyone offer a plausible explanation as to how Retribution was stolen? Not only stolen but replaced with a fake. By all accounts Retribution is a pretty unique sword so a counterfeit would have to be forged which would mean the forger would have to have access to Retribution to study or enough accurate knowledge/description of the sword to make a forgery that would fool Kylar. A big issue is the weight of the sword. Because of it's magical properties retribution is much lighter than a normal sword of the same size. That weight difference should be enough to tip off Kylar of a switch. Speaking of the switch, Kylar thinks it was stolen when he was walking through some town. So the thief would have to take Retribution off of Kylar's back and replace it with the forgery without being noticed. Also, the ka'kari warns Kylar to duck when an arrow shot by Scarred Warble is speeding towards him but doesn't warn him of a thief sneaking up behind him?
So any ideas?

[Peter]

Um, pretty sure Kylar can use illusions while he has Phil. The Mask of Judgement is an Illusion sometimes, dpending on what Kylar wants it to be.

But what's that got to do with how Retribution was stolen?

[Justin G]

Ya in shadows edge the sword smith says something about it having a diamond edge making it indestructable. But it is just the shape it was put into because lures can take on whatever shape.

[Peter]

Shadow's Edge 184. As Justin mentions tho, Iures can change shape, just as much a Curoch so it doesn't really matter at that point.