So since nobody logged in in my web account I'm quite sure that he did not hack me in any way.
Did that guy have any Lua scripts on his server? For instance one pretending to be a U.S.G.N. service and asking for the U.S.G.N. password? ... (aka phishing)
What Chingy said is also true. There are many hacks and cheats out there which just read your login data and send it to the creator of the hack. Never cheat if you want to keep your account for yourself. I warned about this many times but people just don't listen.
(actually running these programs can potentially do much worse things to your entire system)