This is a tired argument. Yes, it's harder with a taxi. Less proof / information about exactly which taxi you were in.
But Uber doesn't get to simultaneously claim to be safer than taxis because of the data being tracked whilst also not using that data to help prevent and prosecute crimes.
It's much easier with a taxi. Taxi receipts helpfully include the taxi cab number, as required by law in most big cities. Taxi drivers usually have more downtime between rides, especially in hotel/airport queues, so they are more likely to discover left-behind items that would otherwise be found and taken by the next Uber/lyft passenger. And finally, taxi companies also have centralized locations for storing lost items.
I've recovered a lost phone by providing a taxi cab number to the dispatcher who sent the cab back out to my location. I was ready to compensate them for the extra trip, but they didn't accept payment. That's something that simply isn't possible with Uber or Lyft.
During the 1.5 year time I was a lyft and uber driver I returned no less than 5 cellphones to their owners. There's even a url in your reciept email that will place a phone call to the driver for this exact situation.
But Uber doesn't get to simultaneously claim to be safer than taxis because of the data being tracked whilst also not using that data to help prevent and prosecute crimes.