how can you find your phone if it's died?

if its completely dead your pretty much out of options but to look around for it. Depending how you had it set up in settings it might have sent its last known location to iCloud.com but if not then theres not much else that can be done. If it was just turned off it might have offline find my network capabilities meaning if its a supported device you can locate it even if its offline by using other apple devices.

Hope that helps!

The old-fashioned way. You'll have to look around for it.

FindMy requires the device to have FindMy enabled, power, and a network connection.