Are you saying that you visited another site apart from RuneScape? If so, I would encourage you to run a full system antivirus scan with the latest definitions on your computer in case of any viruses and/or malware if your account security has been compromised.
After ensuring that you have secured your computer, I would suggest you change your password and other essentials. This page offers great advice for further account security:
Account Security Advice
.
In regards to the lost items, I'm afraid Jagex does not replace lost and/or stolen items.