Maurice Hughes, 26, jumped into the Vauxhall Astra in Albert Road and drove off, despite the driver trying to stop him.
He handed them over to his partner Natasha McDonald, 27, who advertised them for sale on Facebook, Luton Crown Court heard.
Hughes, of Wigmore Lane, Luton, pleaded guilty to robbery on 10 December and McDonald pleaded guilty to possessing criminal property at an earlier hearing.
For Hughes, Dan Hart said he had used minimal force. He was out with his brother looking for scrap metal when he came across the driver.
Man charged after £14.5k of cannabis seized at drug factory in Luton home
Plans to protect Luton parks being drawn up because council is 'ignoring' its own local plan says councillor
Picture shows aftermath of field fire in Sundon Park Road in Luton
Luton's Wigmore Park needs your vote in contest to find the nation's top green spaces
Youths spotted deliberately damaging fencing along the Luton to Dunstable busway
Hughes came from a travelling background and had difficulties with literacy and numeracy, he said.
Stephen Moore, for McDonald, said she had a health condition and three young children. He said she had played a minimal role.
Judge Richard Foster told Hughes he had committed a “despicable” offence on a vulnerable worker who was out on his own. He passed a 1 year Community Order on McDonald.