Their breakup affects him profoundly.
It is most fortuitous that an experimental device was developed to send people back, theoretically speaking, up to five years into the past. Gus reads enough positive testimonials to give it a try. When the device finally arrives, he uses it successfully.
The day of their original meeting comes and goes. She walks by, he hesitates; they don’t speak. He gathers the courage to meet her a few days later, but Amy rejects him this time.
Boy, when that lousy company opens up in a few years, he is going to leave them one nasty testimonial!