I can see this scam being insanely successful with a 2 party scam team. But alone I'm just still mind boggled. Like I assumed once you clicked out of trade it exited for both players not just one. Assuming that he would have to cancel his trade window to be able to pick up your item.
If there was 2 people though I could see it like person to be scammed will be called Bob, Scammers will be Jake and Tom. Jake wants to get item from Bob. Jake has Bob drop item and opens trade window with gold in it. Tom comes in and steals the item from the ground and disappears. You assume Jake did something when in fact he just opened trade window and put in gold or the wrong item or whatever excuse he would use to not continue the transaction.
Wow,not to be mean, but heck dude.. I could smell the scam on that the second he said to drop it on the ground. It's an old trick in many online games.
Sorry, but wow... I feel for you, but hey...this is how we learn.
Secondly, if he's really a 'scanner', I've got some stuff I needed scanned, like in yesterday already.
Jokes aside, I'm sorry this happened to you and hope it doesn't make you lose all your trust in people, just know how to recognize bullshit. It's a huge loss, but it's a valuable lesson. Take it to heart and shake off the gold you lost. No point dwelling in the past.