hmmm... just a suggestion, and possibly a silly one, but if you put lanyard holes through all your knives, then threaded a small chain/steel cable through them all, it would stop anyone "absent-mindedly" walking off with one while still allowing people to handle them. (I'm assuming that you allow people to handle your knives when on display).
It's a real pity that such a beautiful knife was nicked some people just have no clue, do they? I hope it turns vampire on them. Or if you find them, it could add value to the knife: now sheathed in thiefleather, blood patina!