CCTV showed Rafael Lykowski picking up the black wallet in the car park of the Jade Cottage Chinese takeaway, in Mansfield, on April 17.
He was traced by his number plate when he drove away in his black Peugeot, said prosecutor Rebecca Williams.
The owner only discovered his wallet, which also contained personal documents and a keysafe key, was missing the next day.
When he was tracked down, less than a week later, Lykowski directed police to where he's hidden the wallet, and told them he posted the documents back to their owner.
Arjun Madahar, mitigating, said Lykowski, a lorry driver with no previous convictions, wanted to apologise to the wallet's owner and assure him it wasn't personal.
"Quite simply it was a moment of madness on Mr Lykowski's part," he said. "On reflection, he regrets his actions.
"It had been in his possession just under a week, and in that time it had crossed his mind to contact the police. But he accepts he didn't do so.”
Magistrates heard that no compensation was sought by the wallet’s owner.
Lykowski, 41, of New Bolsover, Bolsover, admitted theft by finding when he appeared at Mansfield Magistrates Court, on Tuesday.
He received a 12-month community order with 100 hours of unpaid work.
He was also ordered to pay a £95 surcharge with £85 costs.