To set the stage, a coworker (let's call him Bob) was fired a couple of months ago. Bob oversaw a pretty large team, was well liked by everyone (in and outside of his team), and generally was seen as the ideal employee. Unfortunately, the only person that didn't agree was Bob's boss (John)–it's not exactly clear why John didn't like Bob anymore, but he claimed Bob wasn't meeting his deadlines/goals and fired him. John then took Bob's job, reassigned about half of the responsibilities (because it was an unreasonable amount of work for one employee) and posted the opening.
John has been interviewing candidates for Bob's replacement and narrowed it down to some outside candidate and another former coworker (Adam). Adam used to be on Bob's team but left shortly before Bob was fired for a much better position somewhere else. It was a big surprise to everyone that Adam wanted to come back after making it pretty well known how dissatisfied he'd been working at our company. In any case, Adam really is perfect for the job and went through the lengthy interview process and was selected as the final candidate. John called to offer Adam the position, and he said, “No. I would never work for you again. You're the reason I left in the first place.” Adam made it pretty clear he'd only applied to waste John's time since he's still friends with Bob.
Panicked, John just tried to call the other candidate and he's already accepted a better job somewhere else. Now John has to start over with finding someone.