did he double-spend the TX? sounds to me like he did. Where he sent it, actually sent it but then double spent the same coins with a higher fee elsewhere so yours wouldn't confirm then get dropped from mempool. Always wait for at least 1 confirmation before sending any goods. I sold a titan to someone in person and we had a chat while pending confirmation.
And i saw everything.. the blockchain TX transaction showing my btc address and stuff.
I think that's a new scamming technique, btw he may also scam gambling websites, since some of them accept deposits with 0 confirmation.
be careful guys..
i will stay alert next time