"One would expect to be told when something like this happens to your underage child. This is a nightmare," the teen's mother told newspaper Arbetarbladet.
The accident occurred early on Tuesday morning in Sandviken, 190 kilometres north of Stockholm. The 16-year-old girl was a passenger in a car driven by an 18-year-old man who lacked a driver's licence.
Just before 1am, the car crashed into another vehicle, seriously injuring a 55-year-old man. The 18-year-old driver has since been questioned on suspicion of drunk driving, according to the local police.
All involved were taken to the local Gävle hospital for health checks, but when hospital staff wanted to x-ray the teen's hands she refused and instead went home - without telling her parents what had happened.
The next morning her older sister saw in a Facebook post that the girl had been in hospital. She telephoned their unsuspecting mother to find out what had happened, according to the paper.
The 16-year-old went to school as usual the next day, but was forced to go see the school nurse, as she reportedly felt pains in her mouth, head and hands.
The family is now angry that no one from the hospital saw fit to notify the parents she was there.
"If someone had called us during the night, mum would have been there right away and then she would probably have allowed herself to be examined in hospital," the girl's sister told the paper.
The family said they were devastated about the accident and what had happened to the injured 55-year-old man, but added that they would report the police and the hospital for not letting them know their child was taken there after the accident.
The police told the paper it was the hospital's responsibility to notify parents. Staff at the clinic agreed a mistake had been made and said they had apologized to the family.
The hospital is also considering reporting itself to the National Board of Health and Welfare (Socialstyrelsen) in accordance with Lex Maria, the informal name for regulations governing the reporting of injuries and incidents in the healthcare system.