LOST ALL GEAR account hack and theft, or a game bug?

I haven't played for about a week, so I decided to see what the latest patch had changed. The first strange thing happened when I launched the game. In the start menu, I was notified that the game was launched from a different location and that I needed to enter the code from my email. It's weird, I'm in the same place as before. Okay, I entered the code and the game launched. BUT, my character's entire inventory from the league disappeared. Everything they were wearing disappeared, including the stones in the tree. All the Divine Orbs also disappeared from the chest. Was this an account hack and theft, or a game bug? Do I need to change all my passwords or not?

This is a hack
from PoE1, and all the items and currency disappeared from the character.

The question is, how was the hack accomplished? The mailbox wasn't hacked. Login through a Steam account. Steam isn't hacked either.