I like the idea of a vacuum cleaner. I would try and fashion some clear thin bore plastic tubing onto the shop vac and give it a try. You may need to put a few holes in the tube to allow the vacuum cleaner to pull enough air but you should still get enough suck that way.
Is the nut stainless, brass or aluminum. Annoying that the magnet doesn't work. I think that you have a good chance with a vacuum pipe. Worth spending a couple of hours on that method I think.
Mark