How To Prevent iPhone From Being Erased

There were numerous times people filmed evidence videos with their phones but their phones were taken by force(not sure whether their phones were iPhones though). Later, under the pressure(maybe from law enforcement) the phones were returned but they were erased or “flushed” so the data on them were all gone.

How do I prevent my iPhone from being erased by someone else if I ever find myself in similar situation?

(Expected result: someone has my iPhone, puts it into recovery mode or DFU mode and tries to erase it with iTunes but whatever they do they cannot erase the data on my iPhone without my password or authentication)