The return of stolen cars

Dad ALWAYS left the keys in everything. Cortina got stolen half a dozen times.
Had a 67 Mustang. Dad took me over to order some dirt bike parts. We go in. No sooner to we shut the door and some clown is in it. Car was found in Newark a week later...with 7 parking tickets. Only way they would release the car was if we paid the tickets, towing and impound fees...even though my dad had the police report...

Did your dad ever figure out why people were taking his cars?