Hello sho85czh and welcome to JustAnswer.
Unfortunately for the situation you are in, there is no law in California which would permit you to park on someone else's private property simply because you have a handicapped parking permit. So, if the place you parked was restricted to parking for customers of a particular business, and you did not patronize that business, the owner was legally allowed to have your vehicle towed and you would not win a small claims
case to recover the associated costs from that owner.
The answer provided by psimmons was correct and I am unclear on why you think he was wrong. Furthermore, not only is psimmons a licensed attorney, he is one of the best legal experts on JustAnswer and is very careful in providing legally correct answers to questions posted here. You have not been scammed and since you were provided with the legally correct answer to your question, I suggest that you accept psimmons answer.
Whoever at DMV told you, years ago, that you could do this, was wrong then and would be wrong now, as what you were told is not now and never was the law. By the way, I am licensed to practice law in California and have been doing so since 1976.