The bag, which contained personal possessions, was taken from the vehicle between 7:40am and 8am yesterday while it was parked in Firrhill Loan, Edinburgh.
The paramedic discovered it was gone when he returned to the vehicle.
Police searched the area and some of the items from the rucksack were recovered around the nearby St Mark’s Primary School.
Officers are now keen to trace a man who was seen rummaging through the stolen rucksack a short time after the theft.
A Lothian and Borders Police spokesman said: “No medical equipment or documentation was taken during this theft. However, the paramedic is understandably distressed at the loss of his personal possessions.
“Anyone who was in or around Firhill Loan yesterday morning and saw anything suspicious is asked to contact police immediately.
“Similarly, anyone who saw the man seen rummaging through the rucksack and can help identify him is also asked to come forward.”
The suspect is described as white, between 18 and 25 years old and wearing a dark jacket, dark trousers and dark shoes.