My old friend Tom was once appointed acting general manager of a division of his company. The president told him he was the only candidate for the permanent appointment, and the job was his to lose.
He lost it.
So Tom went back to his previous job as a department head, realizing he’d missed some important elements in the opportunity but unsure as to quite what they were.
He left the company a few months later when the new guy turned out to be a terrible boss – ignorant, interfering and autocratic. Most of the other department heads were gone before Tom.
It took a while longer, but the new general manager was flat-out fired.
You don’t get to go back, though. Tom apparently wasn’t considered again; they never contacted him, and someone else was appointed.