Reminds me of the time I put a Stihl chainsaw back together after a major take apart/repair.
Saw ran great afterwards and when I was cleaning and storing tools I found a important looking white plastic piece in the bottom of a plastic tray that had been holding some of the chainsaw parts/pieces. It's color and texture exactly matched some of the chainsaws pieces. I removed side covers on the saw and could see similar looking plastic, I went to computer and carefully searched the IPL, finally posted a picture on here and the model of the saw.
Day later no response, so I asked one of the expert Stihl guys in these forums his opinion. He said that is not part of that saw.
My brain finally kicked in gear thinking back and I had been working on a washing machine about 2 weeks before and using that container to hold parts/pieces and had overlooked getting all the parts/pieces out of the container.
Could not get the Kenmore white plastic washing machine part to fit into the Stihl chainsaw.