That guy that said there was a security breach was talking about a problem that had already been resolved, and it didn't give access to passwords unless they clicked on a link they shouldn't have. It was a type of phishing scam.
Even though what affected you probably wasn't the exact same scam, your situation does sound like someone got access to your Fiverr account info and possibly your PayPal info. Some of the ways people try to get your info look really legitimate, so maybe it was still a phisher. Unless someone you know had access to your info or knew you well enough to guess it, there aren't many other ways for it to happen.
I hope you get it resolved, but I wouldn't count on it. It's pretty difficult to get funds back once they've left Fiverr. Even if you accidentally withdrew your money yourself, it can't be transferred from PayPal back into your Fiverr account.