Here’s my take on this. Finding a dead iPhone presents a mixed bag of possibilities. For newer models (running iOS 15 and up), the phone can enter a low-power state and remain findable on the Find My network for several hours after it appears to die. This is a significant advantage. However, for older models or once that power reserve is depleted, it cannot send a live location.
In that scenario, your best bet is checking its last known location via iCloud or the Find My app on another Apple device. This will show you where it was right before it lost power. While it’s an incredibly useful starting point for retracing your steps, you have to consider that the phone could have been moved since.