I read about 2 sentences of your post and stopped. Why? Because YOU screwed up.
Police have no duty to tell you the truth. Ignorance has never been an excuse to violate the law and respectfully, you were ignorant.
IF you even remotely thought you had anything illegal, or not, you should always say NO to police. Procedure he says? Here is your procedure. First, make a duplicate copy of your car door key. Insert that key into your wallet. If ordered from your car by police, FINE. Just as you exit your vehicle "click" the locks and lock your doors. If he says WHY, say nothing.
Let him do whatever he wants to do. Everything his procedure may be, fine, who cares because you have a procedure to, its called "your constitutional right to keep your mouth shut.
Bottom line: Let them get a warrant to search your car. Your car is LOCKED. Let THEM do anything they want to do and take names. Once it all is over, save pennies and within one year, walk into a federal distrcit court and file suit against the police officer "INDIVIDUALLY", not the city, respondeat superior or such. Your object is not motivated by money, as a lawyers objective is. A lawyer has bills to pay plus student loans. Read, learn grow a set and file a civil action against police officer(s) INDIVIDUALLY. As long as your case is not held to be frivolous you will not ever have to pay attorney fees, even if you lose. In the end whatever money you had to pay, or whatever inconvienience you had you can multiply by 10 at least and in the end you have won, even if you lose.
If you want to make someone angry, tell him a lie; if you want to make him furious, tell him the truth. All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident. - Arthur Schopenhauer Philosopher, 1788-1860