It turns out Willow, the cat who turned up in New York five years after she ran away from her home in Colorado, didn't make it across the country on her own. Many theorized that Willow was adopted by a new owner, as she was very healthy when she was found (and lacks the opposable thumbs necessary for hitchhiking). A reader sent this tip to Gothamist:
I had Willow (aka Molly) for 3 months, while her NY owner was away for work. He fell in love with her on a ski trip when she was a stray in Colorado, and flew her back to Brooklyn, thinking she was too amazing to leave behind. She was vetted prior to flying, and none of her history came up. While in Brooklyn she was loved and very spoiled...she's had quite an adventure, but there's no great mystery behind her travels. Willow is a lovable cat who happens to fly well. She was brought to the shelter by someone who loved her very much, but was unable to give her all the time and attention she deserves.
I'm sure her Colorado family knows how extraordinary she is, and I am so thrilled she's able to go home.
You may want to add "adopted by a loving businessman from New York" to your list of things to tell the kids when a pet passes away.