At Great Falls, your "contraband" can be voluntarily surrendered shipped ... KRTV: Great Falls airport offers new shipping option for passengers In the context of "hunting knife or something like that, people hate to throw them away", this really didn't sound like the usual TSA issue. I'm surprised the fee-loving airlines haven't implemented "retrieve your luggage to check a knife you stupidly left in your carryon" fee.
nahhhh. that's for small potatoes. For really important stuff, say small nuclear devices, you're better off paying a TSA clerk to ship it for you on your own flight. Contact your local drug lord to determine the going rate.