Many officers were diverted from work on other cases during the 36 hours Joanna Grenside, 25, was missing and in the following two days when detectives believed they were still dealing with serious allegations.
Yesterday magistrates at St Albans were told that the operation, which involved a helicopter and an underwater search team drafted in from another force, cost more than pounds 20,000.
But Pat Larner, the magistrates' chairman, said a 12- month conditional discharge, with pounds 100 costs, was sufficient punishment after reading medical reports that Miss Grenside had been suffering from the eating disorder bulimia and could not face the parties and food that went with Christmas.
Afterwards Miss Grenside, of Harpenden, Hertfordshire, who admitted the charge, declined to comment except to say she was pleased that the affair, which began 10 days before the Christmas holiday last year, was over.
Patrick Fields, for the prosecution, said Miss Grenside's colleagues at Harpenden leisure centre, where she was a fitness and aerobics instructor, became worried when she was late for her evening shift and soon found her Ford Escort abandoned in the car park. Police quickly found her rape alarm, only later discovering she had deliberately discarded it. Initially Hertfordshire police believed she had been kidnapped and set up an incident room, instigated a massive search of the area using dogs and eventually hired the neighbouring Thames Valley force's helicopter and underwater search team.
In all, Mr Fields said, 1,800 hours of police time was invested in the search operation which had cost pounds 20,387. She turned up at the sports centre at 7am two days later, dishevelled, covered in mud and looking shocked, claiming she had been abducted and held prisoner.
She told police that she had been sexually assaulted and later that she had been raped. But because of her distress officers stopped questioning her over the weekend. However, other inquiries revealed that exactly one year earlier, a former colleague of Miss Grenside's at a casino on the Gold Coast in Australia had also faked her disappearance to get publicity.
'When the interview restarted officers made it clear to Miss Grenside that she was no longer believed,' Mr Fields said. 'Almost immediately Miss Grenside broke down and admitted the whole thing was a hoax she had staged.'
Mr Fields said that Miss Grenside had suffered anorexia when she was 16, but this had developed into bulimia, a disease in which victims eat and then make themselves vomit to avoid gaining weight.
Michael Allan, for Miss Grenside, said that as she worked at the sports centre the disease had grown worse. But, he added: 'I don't think to this day that she understands why she did it. It's rather like a snowball, it rolls along.' In mitigation, Mr Allan said that Miss Grenside had since embarked on a course of treatment.