Police are appealing for information to establish whether a man who arrived at a Derbyshire hospital had been hit by a car.
The 22-year-old man admitted himself to Ilkeston Hospital but had no memory of a collision when he arrived, Derbyshire police said.
He was then transferred to Derby Royal Hospital suffering with bruises to his head and ribs - injuries consistent with him being struck by a car.
The man had been walking along Heanor Road, Ilkeston, near its junction with Shipley Common Lane.
He then remembers waking up on the kerb and walking to Ilkeston Hospital, police said.
Police investigating the incident, which happened at about 8pm on Saturday, November 29, want to hear from anyone who was driving in the area at the time.
Witnesses or anyone with information is asked to call should call Derbyshire police on 101.