It's not just where the car was when the picture was taken but also where the photographer was when the picture was taken. I can take a picture of your house from the street or sidewalk and do whatever I want with it and own the copyright to the photo. Which is why the papparazzi can climb a tree outside someones house and take pictures without it being considered trespassing etc... Although how papparazzi photographs are taken and published fall under fair use news/informational provisions.
If the car show in question is in a public place, you can't keep it from being photographed and technically the photographer can copyright the image and you have zero recourse. If the car show is on private property then it is up to the property (land)owner to enforce any sort of photographic limitations or restrictions/permissions. You as the car owner are again powerless (unless you also happen to be the land owner and the photographer was on your land when they took the photo).
All that being said, the photographer that asked your permission and then asked you to sign a release was covering his posterior and satisfying a requirement that may have been, and is often, set forth by publishers if he ever plans to publish a book of photographs. The person that took the photo and then turned it into a card that she most likely self published did not technically need to seek permission to use the photo of your car on her own cards. The "right" thing to do, in my opinion as a professional photographer, would have been to seek your permission first as the other photographer did, especially if her plan from the begining was to use on her cards when she took the picture. On the other hand, if she took a snapshot of your car because she liked it and then later while thumbing through her photographs decided to use it on a card that she made and self published, she should have an effort to find you and give you a copy of the card. If she tokk the photo at a local show then it's usually not hard to keep an eye out at other local shows and find the car and owner again.
If you look on ebay under Triumph TR8 (item number 120623056762 for example), you will find a refrigerator magnet with a photo of my TR8 on it. I did not make, and am not selling the magnet. I contacted the seller and asked them where they got the photo of my car and that I would have appreciated at least a request of permission. I knew that the only place where I had posted the image was on forums where I was clearly identified as the owner so contacting me would not have been difficult. Doesn't mean that it hadn't been transferred to another area or that google photo search still wouldn't pull it up. I did not watermark the photo as copyrighted, even though I can prove I have the original image and try to only post images at no more than 72dpi (low resolution) to limit non-web usage. I was both surprised and flattered when I first saw the magnet selling with a picture of my car that I had taken. I contacted them more out of curiosity than anything else, curiosity in how they would respond. The apologized for not getting permisiion first and offered me a free magnet. Strangely enough, that was all it took to satisfy me. I still get a smile whenever I see it on ebay. Considering that they are selling it from Thailand and they used a noncopyrighted image they could have told me to pound sand and It would have been a long legal haul to get any recompense. Some fights are not worth fighting.
Bottom line: She shouldn't have lied about having a release but she can use the photos she took of your car in a public place without your permission as she owns the copyright of the photo. Yes you own the car but when it is in a public place you cannot control the use of images taken of it. Your car has no right to privacy and no protection of privacy afforded to it. By taking the cards without paying for them you could be charged with petty theft. Letting you walk away with two cards was an easy way to get you on your way. Like I said earlier, some fights are not worth fighting. You would have to prove harm or defamation to you personally from the cards being published with images of your car without your permission to stand a chance in court. In order to do that you would also need to prove that the image of that car could be linked to you personally in a way that could cause defamation or personal harm.
Releases are a good CYA to attempt to prevent lawsuits (but are no guarantee).