Relatives of a man found dead in his crashed car days after he went missing said they had earlier told police where to find the vehicle.
Martin Kent's MG Rover was discovered in a ditch in Leicester on 16 December.
A friend spotted an overturned car in the area on 13 December, a day after the 24-year-old went missing, and the sighting was reported to police.
But officers were unable to find the car. It was spotted when other friends went to look for it, said his family.
Mr Kent's friend Jason Jones said they decided to search for the car themselves after the driver who originally spotted the car phoned to say it was still there when he passed through the same area, on Soar Valley Way, three days later.
Mr Jones said: "We parked up in a lay-by, walked backwards, found the trees collapsed and an exhaust, and a scorch mark or two on the grass.
"We just knew in our hearts then, the worst. Immediately we got back in the car and rang the police and they were out within minutes. I don't see why they couldn't have done that themselves on Monday."
Leicestershire Constabulary said it had voluntarily referred the matter to the Independent Police Complaints Commission (IPCC).
It will examine the thoroughness of the searches carried out and the potential impact on the Newfoundpool man's chances of survival.
Mr Kent's partner Aimi Deacon said the family were "distraught and angry" at the thought that he had died alone in the cold.