That item is called a "PAD WEAR INDICATOR PLATE" although I tend to call them noise makers.
A Toyota dealer did my front brakes in 2012. They used Toyota organic pads. I think they must have discarded the originals. Not sure they were there. $613 oil, rotate, brakes in 2012, so probably that was rears also... So they apparently discarded all of the noise makers. They also did not reset the oil reminder.
Today I had my front and back brakes done with new Autozone premium ceramic pads. There were no noise makers there. So I have none. I had been relying on those indicators to tell me when my pads were worn down. No warning, so I was scraping metal. The rear also did not have those noise makers. I had the work done in my driveway, for less money of course.
The service manual shows them, front and rear. Page BR-53 for the rear. Page BR-38 for the front.