EFS 18-75 mm - unknown piece in disassembly

My wide angle zoom lens became stuck a few months after the lens picked up a rattle. I took the lens apart based on this fantastic tutorial. However, as I got near to removing the core of the lens from the large outer ring, a little piece fell out. It has no markings of having been attached via screw, though it does have two holes.

While I'm sure the piece was the source of the rattle, I have not been able to figure out what it is or where it goes, so I have not yet reassembled the lens.

I've attached a picture of the piece compared to my rather average size index finger. Any help would be greatly appreciated.

Cheers,
Beau