A pair of trousers catching on a lever in the wheelhouse of the RMS Mulheim allegedly caused her to run aground off the Cornish coast.
Coastguards say the Mulheim will probably break up in the Autumn
The vessel was carrying 2,200 tonnes of scrap car plastic when she ran onto rocks near Land's End, on 22 March.
Hundreds of tonnes of the cargo, which was destined for a landfill site in Germany, escaped into the sea after the vessel ran aground.
The details of the incident are cited in a safety digest from the Marine Accident Investigation Branch (MAIB).
The MAIB's safety digests do not name the vessels involved in accidents, instead they issue safety advice based on information gathered from preliminary reports.
But the report does refer to a ship which was wrecked in March with a full cargo of shredded plastic waste.
"The loss of RMS Mulheim was the subject of an MAIB preliminary examination," said an MAIB spokesman.
"Although the reports of all MAIB investigations are published on completion, the MAIB's Safety Digest does not name the vessels involved.
"It seeks to promulgate the lessons to be learned from a wide range of accidents not necessarily subject to a full investigation," he said.
"It appears the chief officer was on watch," David Barnicoat, Falmouth Harbour Pilot, told BBC Radio Cornwall.
"He was sat in a chair and when he went to get up his trousers caught in the chair's lever and he fell over and knocked himself out."
The report says by the time he came round the ship was closing in on the shoreline.
The cost of the operation to limit the environmental impact, protect the public and salvage the cargo is estimated to have cost more than £1m.
But Cornwall's Emergency Planning Officer, Steve Winston, said he is confident the money will be recouped from the vessel's insurers.