So ask him to hack your account then if he's so smart, i very much doubt the guy hacked anything, actions speak louder then words when it usually comes to hacking / hackers.
Or perhaps one of your users used a bad password, i mean how many people use their starsign or dogs name etc, there's always a chance he guessed a password and decided to make wild claim.
You can always check the security sites.
I posted a question a while back
here.
You could check out those sites for any possible exploits and then verify them here ""IF"" any.