It sounds like your account was compromised. I would make sure to change your password as soon as possible to prevent this from happening again.
Per the
Terms of Use, it is the account owners responsilbity to keep it safe.
A. Account security
The account owner is responsible for the security of the account and that it's sufficiently protected. Note that Nostalrius staff does not recover hacked accounts. You should:
Never share your account information;
Have a unique and complicated password that does not exceed 16 characters;
Connect yourself from a secure computer and network;
Never download unsafe files that might contain viruses/malware.
In terms of item restoration...
III. Character/Currency/Item restoration
Nostalrius staff will not recover any lost characters, regardless of circumstances. We do not recover any lost items or currency except raid items with the rarity of Epic and above which can be restored in the case of a Server crash/roll-back, providing an in-game ticket is sent to us which fulfills the following conditions:
We will not restore the lost loot if the ticket does not meet all the requirements. Falsified information will lead to immediate account closure.
Exact date of the raid;
Screenshot of the raid ID;
Screenshot of the loot & complete list of raid members;
Name of the player who received the item.