My son misplaced his phone but doesn’t have the Find my. Feature set up. Is there anything else that can be done?

Not really. When my wife can't find hers (it's on a different Apple ID than mine and I don't think Find My is active) I just call her via FaceTime to see if we can find it somewhere around the house or in the car.

You can call the number.

To give a spark of hope, another poster asked how to contact the owner of an iPhone they found on the street to return it. Ask if the police or Apple have been contacted.