Sorry, Cerby. People never just randomly move on. It's human nature to have something waiting before making the leap. If it makes you feel better, everyone in your position, the person who left them had someone else there or waiting. Whether the person ever finds out or admits it to themselves is another story. So what happened to you happens to everyone. It sucks and doesn't feel good, but I promise you there's TONS of single women in your age group looking. They may have some baggage, but we all do at some point in life. Move forward, she wasn't 'the one'. No biggie, someone else can be now.
...as ancient astronaut theorists would suggest