Driver kept lost phone

My daughter accidentally left her iPhone in an Uber ride. We could see its location up until yesterday, when it went offline. We added a contact information and offered a reward in the “lost phone” message, with no avail. It’s been difficult to get assistance from Uber, but we finally got the driver’s phone number.

I realize the chances of getting the phone back are slim at this point, but I want to try. Assuming he’ll block me once I reach out, I have only one shot at this. What’s the best next step?

TYIA