Does apple do any tracking by serial number for lost/stolen iPhone?

I understand the Find my iPhone feature and the lost phone solutions. I have put my phone into Lost Mode, but it is "offline" which leads me to believe someone who found it has it turned off.

I left it in a Lyft ride.

it had nearly 90% charge and sufficient battery that a cellular signal should have the phone in "online" mode. Im not understanding why the phone is "offline".

My question: If someone is trying to reset the phone or bring it to someone that can hack it and erase it, does Apple offer any services to track the phone by serial number in case someone is successful in resetting the phone? As to prevent them from using it. It is an iPhone xs-"unlocked".

Can anyone respond with knowledge around this?

Thanks,

Kenji