can post whatever you like. Just remember that a post like this can really affect future transactions for the person. Unless he cheated you somehow keep it to yourself and just don't deal with that individual again IMHO.
His friend chimed in and gave some reasons. Whether they are true or not I don't know nor do I really care since I would never have put myself in this situation. Shit happens in life and keeping a random person who you traded a few emails with about parts informed is not always a priority.