Its a con for sure just one of many, and so frustrating. They know full well you can't prove anything and even if you tried it would be stressful and more than likely more expensive to do so. People are sick to death of being conned /ripped off. My only advice is do what I always do ( without fail) if you use any car park, drop the ticket in your glove box, and leave them there for at least 3/6 months. Its not something that you think of doing at the time, but just try getting into the habit.