Im confused. So they hacked your account, but only chose to trade your existing currency for NXT. That's kinda weird. And then only after you changed the password did you actually end up losing access. Even more weird. Sorry this story just sounds a bit off tbh. I'm sure there have been many people that have been hacked on Poloniex and other exchanges, but if that happened the first thing that would happen is the account would be cleared. Anyhow sorry if this is true.