I'm with Walt on this one; there is no solder in the engine,
AFAIK. The only thing that I can possibly think of was that someone tried to repair a leaking (engine mounted) oil cooler by soldering it up with household solder. Since it doesn't appear that the trash went through the oil pump, that leaves a very limited amount of things that could have possibly happened. The only things that are after the oil pump but before the oil galleries are the engine mounted thermostat and the engine mounted oil cooler. The external oil cooler(s), lines and thermostat are on the scavenge side of the pump and if soldered up, the trash would have ended up in the oil filter or the oil tank, but even then, nothing that big could have passed through the oil filter bypass. That's my wild ass guess. Other than that, I'm at a loss to where it all came from.