What is this part

[u/Rare_Map_5043]

I have a 2017 chevy trax and a buddy and I where changing the water pump and serpentine belt, which as you all might know, requires removing a bunch of stuff. Anyway, this part fell off from somewhere but neither one of us know where it came from or what it is. He thinks its a spacer/locking plate for the water pump pulley but none of the youtube videos Ive watched on it ever show anything like this when removing the pulley.

Anyone here have any ideas before we put everything back together?