Finding someone else's device
Can a device using a different Apple ID be located using Find MY?
iPhone 5s, iOS 12
Question marked as
The Find My app is intended for your own Apple ID account.
To use the Find My feature for other accounts, try having the other user sign in with that other account to the www.icloud.com website, so they can use your device for the search. It will likely default to your own account, but there is an option to “Use a different Apple ID”.