The same thing happened to me on a french server 2 days ago, received an email telling me my email account have been changed. I was in game and disconnected, unable to reconnect.
All the stuff on my 3 lvl 80 has gone (vision of the mysts, arah stuff, human T3, …).
My guildies tried to speak to the one that logged in my account, he said in french : “You ’ll tell him thanks, ok?”
No other IP connexion on my email, no trojan (spybot, avira, adaware, hijackthis found nothing) and never told my password to anyone (only use this pass for guild wars), nobody have access to my pc…
Feel very disappointed, think i will not continue to play gw2…