While searching for scholarly articles about Yorkies, I came across a recent article about a Yorkie that swallowed some toy magnetic balls, sold under the name "Buckyballs." Magnetic balls are extremely dangerous for Yorkies (or children, for that matter) to swallow, because even if they are swallowed separately, their magnetism is so strong that they will seek each other out and perforate the digestive tract like a bullet. The Yorkie who swallowed the Buckyballs died a couple of days after surgery. The article is thankfully behind a paywall so you can't view the x-rays, but you can read the abstract here:
Multiple magnetic gastrointestinal foreign bodies in a dog .
I thought that this was just a freak accident, but it turns out that Buckyballs, which used to be widely sold, have been completely recalled due to children swallowing them. Here is an article in the popular press about their recall:
How Buckyballs Fell Apart .
Please search among your children's toys, and if you find any magnetic balls, discard them IMMEDIATELY.