Ok I agree in running her if you didn't find that bit of the spring. If you dropped the sump pan I would wonder what you found in the pick up screens especially the front one. If you didn't check I wouldn't pull her back down especially if she is all together. If it got to the screen the mesh is too small for something like that to pass. Figure most people ride a little or a lot before they figure out it might be broke. It could have been stuck in the clutch cover when you first opened it especially with a gasket lip on it. I'd put her back together and go spank good. Maybe the next oil change if I was worried I'd be dropping the sump pan for another look. The gasket is cheap. Remember since you have had the sump off you could have already disposed of it during that process.