"I learned to drive in it, my grandmother taught me how to drive in it. So it's really special to me," he said.
"To do such a thoughtless thing while someone is recovering in hospital, in a time of need, is really horrible.
"It's a real downer at the end of what's been a tumultuous time. I'm really cheesed off."
Mr Stevens said he purposely parked the car near the lifts in the building as it was a well-lit area and he assumed, because of the numbers of people going in and out, that there would be security cameras. The hospital has reviewed its footage but said the car was not in any of the shots.
Mr Stevens said he was concerned about the person or people responsible for the damage.
"It shows a total disregard for your fellow man - especially at a hospital."
The timing was also terrible.
"The car was such an institution in our family. It's a real connection to my childhood and my family.
"With me sick and ailing and all the death in the family, just having that special connection to the family is something really important to me at the moment. To do what they've done is just the lowest of the low."
If you have any information, contact the North Shore police.