Cheated
It turned out Heather had been in a relationship with the man she met at this fair for a year. The other man hadn’t known about John any more than he had about the man: they had both been fooled. Neither of the men knew that their girlfriend was in a relationship with someone else.
This was quite a downer for John. He had a bright future ahead of him and was deeply in love with Heather. The unknown man stomped out of the room and John never saw him again.
John angrily demanded that Heather leave. She did this, leaving John alone in the room.