Marc Scott and his partner has just welcomed their new baby when he was told that the second-hand cars had been taken from the forecourt of MPS Motors in Hunslet.
A group of around seven men drove the cars away from the garage after stealing keys from the office in a 'Fast and the Furious'-style break-in.
"I was in hospital and was just about to cut the cord when my phone started ringing. There'd be more chance of me winning the lottery - it's a complete one-off," said Marc, who lives in Ireland Wood.
Two men broke into the premises at around 7pm on Tuesday night, only half an hour after Marc had left to attend the birth of his child.
"We don't normally keep the keys in the office, but as I left in a hurry I asked a colleague to take them home, and unfortunately he forgot to. It's a horrible coincidence."
As several of the cars had already been sold to new owners who had paid deposits for them, Marc has been faced with having to refund customers, and is unsure whether his Low Road dealership will survive.
"I don't know what to do - it's been four years of hard work. Do I carry on and pick myself up, or just get a job?"
In CCTV footage taken from the business's offices, two men are seen entering through a window grille before spotting the keys. They then make a phone call to associates, and around five other men turn up and begin driving the vehicles away. By 2am, they had stolen 15 used cars, as well as logbooks and paperwork.
"They also took keys to another 15, and we've had to let the tyres down and remove the valves to stop them being taken too.
"We don't know if it was a group, if the cars are in the same place - they drove off in different directions. They've probably changed the number plates, and they might be in a storage unit somewhere. We've been driving around all day looking for them."
West Yorkshire Police confirmed they are investigating a burglary and theft of 15 vehicles from unoccupied premises. A spokesman said:-
"We are making inquiries about vehicle movements, and it's likely many of them will have different registration plates by now. It happened over a period of several hours and anyone who saw anything suspicious should contact us on 101, quoting crime number 13170119013."