After you've tried all these tricks and they don't work....
Buy a small bag of Kingsford Charcoal--not ReadyLight type. Regular good 'ol charcoal.
Cut the bag open evenly at the top just below the sewn seam, crush coarsely (appx. BB size) about 5 of the briquettes, setting aside the result...open the knife and lay it right in the bag, centered atop the still briq'd charcoal remaining inside. Dump the crushed charcoal on the knife, covering it about 1/4" or so deep....roll the bag down tightly a turn or two allowing an air dome to remain in the bag, and seal it. Every now and then when you walk by it gently squeeze or pat the top-dome of the bag to move a little air inside (2-3 times a day is enough).
Leave it for three days. See if the knife still stinks. If it does, dump some cheap ground coffee into the bag with the knife and charcoal, repeat the process and open it after a week....
If it still stinks research whether FRN is subject to odor absorption. If so, the knife was likely stored somewhere around bulk chlorine or similar.
If the charcoal doesn't work in either case, it's unlikely you will get the smell out without something specialized involving expense....IF you wanted to go further.