Here's my $.02.
As already mentioned, he probably needed some quick cash. After a week you didn't go back to pick up the $300 winch. He had someone there to buy the ENTIRE Jeep. I bet they had cash money right then and there. Sucks that you didn't get it but I would have done the same thing if I was in his shoes. At least he called and told you it was no longer available.
I've sold a good bit of junk in my day and have had someone pissed at me for not "holding" it for them. However, I never agreed to hold anything for anyone. First come, first serve because I don't give a rats ass who buys my parts. As long as they're selling with no B/S drama I couldn't care less.
Just learn from this experience. An ATM is never too far away.
