I think it was standart on zx3-zx5. If you have the door lock switches inside the car, well I think you should have it. But that's my opinion.
I had a base 2003 SPI SE sedan and I had keyless entry, so I think you have it ;)
2012 White Mitsubishi Lancer 2.0L : New car
2005 Black Ford Focus zx5 SES : Trade In
2003 Arizonna beige Ford Focus SE : Sold