Did I have USB debugging on or off?
Having USB debugging (adb) enabled on a device is not a security problem anymore since Google introduced the adb authentication using public keys with Android 4.2 (or was it 4.4?).
Since that time adb does not work when you connect it to a PC it has never been connected before.
The device does not allow adb access unless the user has authorized the PC as allowed using the dialog that appears on the phone when connected via adb. This dialog can only be seen and answered when the device is unlocked.
Thus a lost or stolen device that is locked can not be accessed via adb.