So somehow OSBot has a leaked database and only you and maybe 5 people have gotten hacked, not the 1000+ other members
It's because of the fact that you use the same password for other forums, you might not admit it now but at least admit it to yourself. If it wasn't that it could have been something such as a keylogger. TLDR; it could be anything.
At the end of the day you're responsible for your own account, you own it therefore you are responsible for it.
You have 6 hours to refund