In the end, he bought the rights to the sign, changed the wording to "Baby On Board" and founded his own company, Safety 1, which sold the now-iconic car decals and other safety gear.
"I don't know if I would have connected so strongly with the product if I didn't have that experience," he told reporter Caitlin Gibson.
By September of that year, 10,000 had been sold — a number that soared to 500,000 per month by June the following year.
The stickers were so widespread that by 1986, they were being parodied by alternative versions bearing slogans such as "Baby, I'm Bored".
Still, the popularity of the little yellow decals persisted — and in 2000, Mr Lerner sold up to Canadian company Dorel Industries, pocketing $US38 million ($A54.3 million).
But in an ironic twist, Mr Lerner, who made his fortune and a career out of a baby safety sign, never had children of his own.
It enabled him to live a life of luxury, and last year he made headlines after selling his plush Miami Beach mansion to DJ Khaled for US$26 million ($A37 million).
Over the years, the origin of the sign has been tangled in rumours and urban legends.
One popular story incorrectly claims the decals were produced after the death of a baby known to the inventors, while others mistakenly believe the purpose of them is to alert emergency services to a baby possibly being thrown from a vehicle after a crash.
"The sign is not for emergency services but more of a notice to other drivers. Anyone using these signs must ensure they are not obstructing the driver's view," a NSW Police spokesperson is quoted as saying on the NRMA website.
Officially, according to Safety 1, the idea behind the sign is to "encourage drivers to use caution when approaching cars with younger passengers".
Lerner has also busted those persistent myths, insisting the entire company was born as a direct result of that one life-changing drive 35 years ago.
