I wouldn't drive the car until you have removed the pins, pads and the trapped anti-squeal spring plate. The latter holds the pins and therefore the pads in place. Can only suggest it was mis-seated when pads were last changed.
If damaged the part you will need to replace is (5) in above diagram, one for each pad pin, and part number MBS1890. I would check pads and pins as well.
I don't think it is one of the springs - it looks more like one of the anti squeal shims that fits to the back of a brake pad.
On later models there isn't such though TBM - check out parts diagram above. I think the spring clips bearing on pins and top of pads serve that purpose.
They're often bonded/fixed onto the back of the pad rather than a seperate item in the old day. I had a set of new pads from my Mrs Hyundai in the shed, and they have shims fitted.
My understanding was the spring clips were to stop pad rattle and to prevent the pins working loose.
From the photos, it looks too large and flat for a spring, and also don't think it possible for a spring to fit between the piston and pad whilst in situ.
