I have a 2004 Mitsubishi Lancer with 270k+ miles. It has so much wrong with it, that I can't tell new symptoms from worsening old symptoms.
BUT! I noticed that the metal bar that holds my plastic oil cap on was missing. I took the valve cover off and found the bar wedged in, away from the lifters.
I didn't think of the nut until I bought a new cap and saw one on the new cap. There's a real good chance that the nut is somewhere in the engine, oil line, oil pan or oil filter. I have no idea what the flow is from there, or if a nut could pass through any of this.
What should I do next, beside shopping for a car?