On a whim I clicked on the "I lost it" topic while visiting him. Early in the game I found it amusing and somewhat "Zen" to see his response: "You never found it."
This time, however, he gave me a shield and told me to be more careful in the future. Clicking on it again and he gave me the keys to the dragon towers! Again and it was the letter from Zenoflex! (Yes, the shield is none other than the Shield of Kilburn).
In other words if you mess up and lose any of those quest items you can get them from the Seer just for the asking.
Of course I hadn't actually lost any of those items. The shield I had long since returned to Wilbur Humphrey and as for the keys and the scroll, I've completed those quests and left them locked up in those three chests in that first room off to the right back in the Goblinwatch Keep along with all the other useless little bits and pieces that are left over after all the quests that I've completed.
It doesn't seem to be useful to get these duplicates. I flew back over to the castle and talked to Wilbur again --- he didn't offer to take the new shield of Kilburn away from me (no bug to give me extra experience that way) ... and I did beacon back over to my cache in the Goblinwatch Keep and the other instances of the keys and scroll are still there.
However, if you ever manage to lose some item that's needed for a quest ... apparently you can get a clone of it from the Seer. He doesn't seem to be quite so omniscient to tell you that you no longer need "it" (or even to know which "it" to give you --- I'm pretty sure he'd've given me a whole set if kept asking; which gives me at least one hint while these are listed as "value 0" and why no shop keeper in the realm will buy any of them off you. (Snergle's axe should, at least, have been saleable).
