How to track my mother's stolen iPhone 15?

My mamas iPhone was stolen over a week ago. I was in school and it took at least 7 hours before she could use my phone to try and locate device. It was dead when stolen so it was not powered on and still says offline. Does she have any hope of getting phone back or can prove to police who has it instead of he say she says stuff the law has said reason for not helping her. She can get into iCloud and has marked device lost is that what she should have done or kept pinging at different times? She has eSIM and doesn’t have place to take regular sim so isn’t that better so no one could just install another card into phone? What’s best advice it getting phone back. She knows who stole who had but law enforcement says it he said she said stuff but she just don’t think she should let him just have it after going through this at least 4 times In past. Yes bad crazy relationship I know but no lying here folks I need help I have no means to purchase another one and to let him keep it. She needs some great advice in finding this iphone15. Is there anyone during the 7 hours he had stole phone that he could have done something to where it will stay in offline status forever?.

[Re-Titled By Moderator]