How do I track a dead iPhone 8?

If you can't see it's location in Find My, because the phone is dead, you'll have to look for it the old fashioned, with your eyes way. I know that's not what you were hoping for, but a dead phone can't share it's location.

See what you should do here --> Mark a device as lost in Find My on iPhone - Apple Support

And this too --> Find your lost iPhone or iPad - Apple Support

In the first link it explains how to put a message on the screen if someone finds the phone and wants to be a good person and try to get it back to you. Sadly, most lost or stolen phones are never recovered.

If the phone cannot connect to the Internet – for whatever reason – it will not be able to report its location via Find My.

If the phone still has a battery charge, and Find My Network was enabled, there is a small chance that the phone's location will show up. In that case, the phone would be broadcasting intermittent Bluetooth signals – even when it was turned off. If another Apple device came close to the phone, it might report the phone's rough location.

If the phone is turned on, and has a battery charge, but has no Internet service, it might still be able to ring. You'd need to have a pretty good idea of where it was lost (e.g., "somewhere in the house") and a way of calling it while you searched in order to try to locate it in this way.

Are you saying that the battery was dead before the phone was lost? If not, how do you know that the battery is dead?

Is it possible that a message of "Offline" is appearing when you try to locate the phone using Find My?

Paradegirl wrote:

The battery is dead and its location is not showing up - What can we do to find it?

This is a hopeless situation. You would have to spot the iPhone using your eyes to find it.