Stolen Phone

If they were not on you can do only this.

Also file a police report its worth it it Might show up.

I hope it was insured and you're able to get a new phone right away.

If Find My iPhone or Find My iPad isn't enabled on your missing device - Apple Support

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If Find My is offline or not working - Apple Support

On the next device setup, find my asap.

Locate a device in Find My on iPhone - Apple Support (IN)

There is nothing you can do with remote technology. The one and only method Apple provides to remote track a device is Find My. If Find My was not enabled, there is no mechanism to track it remotely.

Report the theft to the police and file an insurance claim if you have any insurance that covers the theft.

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support