Small Engines (Lawn Mowers, etc.): Briggs part, gear shaft, compression release

Question
Have Briggs Model 258707, Type 0126-01, Code 92100830.
In disassembly, found cup/cap which appears to be size and shape to fit on end of valve stem but discovered deeper in the engine where it had fallen.
Parts list doesn't appear to show this part.
Any help appreciated in identifying this part.
Thanks.

Answer
This is very hard for me to explain on here, but I will try. Was it found in the sump/oil pan? If so I think it is the cap that goes on the end of the assembly for  compression release. There is a gear which moves up and down with two little arms, I think the part you mentioned goes on the end of the gear shaft. Like I mentioned this is extremely difficult to explain on here. Doesn't this cap type thing also have a small rim around it like a tiny hat?........Tom