uber driver refuse to return items

So as always used uber as u always thought I could trust them untill now. Sunday I drop my phone on the back seat im pritty sure he saw it as he couldn't get my stuff out the boot on sidewalk fast enough to jump in and drive off. After reporting it to uber was told to wait 24 hiurs for driver to contact me. That did not happen and they just wont give me his details. I dont earm much qnd that phone is just two weeks old . Now have to borrow a phone as I get no help from uber.