This ^
As a computer science student, I know from a security standpoint that hacking is not limited just to executed software. It's indeed possible that a hacker could have received your personal information over your network. Highly unlikely, but is probable. Although you did state you have been away for quite some time...
Also keep in mind, antiviruses can only prevent by detection. It's possible that you do have a keylogger on your machine and your antikeylogger does not detect it. Programmers like me have a fun time obfuscating and hiding software so that it cannot be detected. It's really not hard to do.
If someone really wants to hack you, they just brute force the account until they can get in. It's not hard to use social engineering to extract one's personal email address. And after they obtain it, they'll keep brute forcing the password until they're in.
Good articles on password security:
Coding Horror: Rainbow Hash Cracking
Coding Horror: I Just Logged In As You: How It Happened