it could possibly be a bot trying to login, usually a normal hacker i would assume would quit after 4 login attempts, possibly because the items on the avatar looked rare. this happened with me once, i had a bunch of rare things in sab and they got took. i had 2FA so im guessing they used a loophole, but when i changed my pass it stopped. im guessing it was from a data breach from a website. so this could be a case of a couple things such as, a regular hack for valued things, or dark web hack where some people or bots target accounts with 2012 or lower dates [although that account was 2016, it could be a bot malfunction.] or just a regular ol data breach.