Possible part identification

I replaced the front strut assemblies on my 2013 today. After getting the wheels off, I hit the 22mm bolts with an impact gun and this round piece fell out from somewhere and landed under the wheel assembly. It looks like it should have something going through it, and it's not broken, so sort of racking my brain on where it could have come from before I got anything disassembled. It feels like a hard plastic, like PVC.

Any chance it may have just been something kicked up from the road and got stuck somewhere?