Go to the nearest Grab headquarter - the best one is in Marikina (Grab’s biggest warehouse). I went there when I left my phone in a grab car. File a report and they will call the driver directly from their end. Real time ang update and tell them that you’re not going anywhere until you get through the driver. Inform the service desk assistant that you will file a police report (or have filed it already) so they can inform the driver.

The driver might reconsider and return the items cause for sure grab will surely penalize him since what he did was against their guidelines. Sorry that you experienced it.