Hello,
I completely understand where you are coming from.
The exact same thing happened to me in November 2019
after a successful streak at the duel arena. I was using my main account which did not have 99 HP for staking and so people were staking me left and right, but I kept winning. After leaving the duel arena happy, I decided to never go back.
Facts:
I did disable my authenticator on November 6th, 2019 in order to switch devices. When attempting to enable authenticator on new device, the page said "Error: authenticator is already enabled on your account." Before going to bed, I tried logging in again just to confirm authenticator is working on new device, client prompts me for Auth code and entering it results in successful login. Thinking my account is secure, with case insentitive password, bank pin and authenticator enabled, I went to sleep. The very next day all of my items were gone and my account is hacked. I received the same response that you did.
Discrepancies:
Jagex claims my authenticator was disabled for several days, before being re-enabled,
despite having tested the authenticator app the same night it was enabled.
15-Apr-2023 00:46:03