If all your stats have been reset to 1, then you logged into OSRS instead of RS3.
If you have your stats, but your items are missing, then someone gained access to your account and stole them while you were away. You should secure your computer and account to make sure it can't happen again.
~~~~ Just another victim of the ambient morality ~~~~
~~ Founder of the Caped Carousers quest cape clan ~~