I have had some narrow escapes myself from losing my pocket knife or my multitool that I had almost too late thought of to put into checked luggage before a flight, and I have heard others regret having to toss nice knives (that they had not thought of because they had always been in their pant pocket) into the bin at security control.
What looks to me like an obvious business opportunity, at least for larger airports, would be a stall near the security checkpoint that accepts such small contraband for a fee, puts it into a padded envelope and mails it to an address provided by the customer.
London City Airport has this service (or it did around 6 years ago). My wife had forgotten to pack her house keys, which had a small pocket knife on a keychain. There was a vending machine that dispensed ready stamped envelopes and a post box.
The servcie isn;t offered at any of the larger London airports as far as I know (and I’ve travelled from all of these more recently). Thought it was a fantastic idea and am surprised it hasn’t been more widely adopted. However, I can imagine there’s an argument that it would slow down security is extremely busy airports.
This has been implemented already, as far as my experience goes - you just go out of the security area and use priority mail to send it back to yourself via USPS. I even had a TSA agent confiscate a bottle of contact lens cleaner and suggest that I could mail it back to myself.
The only thing they don’t have is a handy kiosk right next to security, but it’s always been available somewhere in the airport.
I was in the Reno(?) airport and they had a kiosk right near the security line. I don’t remember the name of the service–it wasn’t UPS or USPS. They had envelopes and small boxes which you could use to mail the stuff back to you. I didn’t look too closely, so I’m not sure how you would pay for the service.
They have one those kiosks right next to the security checkpoint at RDU (Raleigh Durham Airport). The prices are exorbitant (I believe a package large enough to hold a medium sized pocketknife knife costs around $40) but worth it if the choice is between missing a flight and throwing out an item with sentimental value or a very high monetary one.