Like Rick (Cazador) had said, you can have some variance between individuals and especially with males, that tend to be smaller and more slender then females, this might be possible. That's also why you can use the other characteristics like placement of the side stripe, spots below the side stripe....number of labials, ect. to make a positive ID. If your count was correct, this would give you a scale count of 17, which doesn't correspond to any of the Thamnophis species that are found in your area. Even ribbons, by the book, have a scale count of 19. The only ones with 17 are T.ordinoides and T.brachystoma...ones a west coast garter, the other an east coast one.