oil pressure disappeared.

Starting your car and letting it run for 10 minutes and then shutting it off and a week later coming back and starting it up for 10 minutes and then shutting it off this all builds water in the oil pan. Known as condensation. If you're going to start the car after it's been sitting for a long period time run it for 30 minutes or more to cook that water out of the oil.
Why don't you put a magnet in the sump of that oil pan or a magnetic drain plug it would have picked up those little wire pieces and you probably wouldn't have this problem.