Admissions error and consequences

I was reading up the Reddit page here, which described a case of admissions error, in which:

1: The person obtained an acceptance for a PhD program

2: The person personally called the university and confirmed acceptance of the program

3: The university then said that they had made a mistake, cancelling the acceptance.

What would be some things that the person can take, and if some of these actions required specific conditions, what would be the conditions be?