I recently got scammed in a trade in Team Fortress 2. I know the person who did it. Is there any way for me to get my items back? Or will I have to live with the shame of my ignorance forever?
No, unless you convince them to "do the right thing," you're stuck. Valve's policy on Steam Trading is very clear on this:
The article goes on to state that making sure you are comfortable with the terms of a trade during the trading process is fully your responsibility.