A young couple from the northern town of Verden found the 9 mm Sig Sauer pistol in a side pocket of the pram after collecting it from nearby Hamburg. They called the police.
Officers searched the house of the 39-year-old seller, who could not explain how the weapon had got there.
"He said it didn't belong to him," police said Wednesday.
(Reporting by Dave Graham; Editing by Matthew Jones)
