There is a pretty hefty spring / clip of some sort on the outside of the caliper, fits into a couple of holes on the caliper and pushes against the slides.
That spring is missing on the other side. It seems like the brakes may be dragging on that side also. Is this just a vibration clip, or does it assist with the caliper returning?
It seemed to me that the spring is intended to damp vibration and prevent squeaks. The last thing you'd want is a spring to retract the piston.
Either way, I'd put it back the way it was.
-rev
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