It sounds like you have fallen victim to a phishing stream. As a rule of thumb, Jagex will never introduce double xp in Old School RuneScape.
I'd recommend following the steps in
Securing your computer
to make sure your account is secure. After you have done that, you should enable the
Authenticator
on your account.
As for your lost items, I am afraid that Jagex is unable to return these to you. Please see the
Lost Items
page in the Support Centre for more information.
If you need additional assistance, it would be best to create a new thread in the
Community Led Account Help
forum, where those with knowledge on this kind of issue are best suited to be able to help.