You can mail it to yourself. There are Dropbox’s at the checkpoint and the agents will help you with it.
Thanks. They very politely gave me four options: check it in a bag, mail it (as you point out), dispose of it, or go give it to somebody who dropped me off. Checking the bag was easiest as Spokane is a small airport and I had the time.
It was very interesting: The two TSA people were kind, polite and helpful to a fault. But the woman at the Southwest counter was a rude jerk, complained to me that I didn’t use their kiosk, and she would help me out JUST THIS ONE TIME.
Then, when I went through the TSA security checkpoint the second time, the agent (who checked me the first time) joked with me “Back so soon?” and we both laughed.