This is why I set up tasker to lockdown my phone under certain conditions, such as: getting disconnected from Bluetooth (like when my phone is separated from me and my watch, my headphones, or the car), getting disconnected from WiFi (like when it's taken from where it's supposed to be), getting a slight jolt from the accelerometer (like getting thrown to the ground or even just a swift tap). My phone may get locked down a bunch during day to day stuff, but at least I know it will lockdown automatically when it matters.