how to find my iphone when lost and offline?

Unfortunately you limited the possible responses w/ “offline”

There is some possibility that FindMy might locate it using another user’s device, but THEIR device would need to be properly configured, online, and on-network for that feature to work.

Your only option is to follow the steps here and re-trace your steps; enlisting the help of friends if available.

https://support.apple.com/en-us/HT201472

They need to be running iOS 15 AND have “FindMy Network” enabled as well as their bluetooth.

NOTE: “FindMy Network” is a new addition to the “basic” FindMy which has been around for several years.

You’ll also need one of your own trusted devices to run FindMy. (i.e. an iPad or Mac signed-in w/ your AppleID)

See more info here:

https://support.apple.com/en-us/HT210515

Devices are not actively / continuously tracked.

Rather they are located “on demand” by the FindMy app.

However, the phone WILL initiate sort of a “Last SOS” when it reaches “Critical Low”

This is location stored in the FindMy network and can only be accessed for 24 hrs using FindMy.

L_Wx wrote:

I misplaced my iphone and its now offline. How can I find it?

The old fashion way you physically look for it.