my phone got stolen a month ago and I Don't know if I had usb debugging on or off(I had enabled developer options in the past and messed around with it a little bit that's why I'm not sure) but I remember,everytime I connected my phone to the computer I had to unlock the phone using my pin and select files or photos in the notification bar to access the files on the phone,otherwise you couldn't Mount phone as a storage device.i never had anything on the notification bar that said USB debugging is enabled when my phone was connected to the Computer. Did I have USB debugging on or off? and if I had USB debugging on could they simply remove the PIN and use the phone as is? I'm worried about my chrome data not about videos photos... Thanks alot
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.