PASSERSBY helped a man knocked unconscious in Beach St, Frankston, 4.25pm, Tuesday 22 August.
Police believe an unknown man punched the victim, 44, and then stole his bike.
The victim had just returned from the shops in Ashleigh Avenue when the assault occurred, possibly on his bike.
However, he had no memory of the incident when questioned by police.
He was taken by ambulance to Frankston Hospital. CCTV shows the possible assailant riding off on a bike matching the description of the one the victim thinks is his.
Anyone with information is urged to call Crime Stoppers, 1800 333 000.
