You should call to ensure that there's no mix-up, but most likely, there isn't one.
That said, you are an ALTERNATE. Realize that historically, Western has been pretty good about eventually offering most people who interviewed a spot at some point or another. This isn't the end of the world. Continue to improve your application in any way that you can (and send in updates if you think you have something they should know about - new awards, new grades, whatever, use your professional judgment) and call every so often to get an update on your status. These things don't go unnoticed. The school wants to offer spots to people who genuinely want them. It wastes their effort and time to offer spots to people who aren't really interested.
Also, you have other interviews. Do well on them because you never know what you might find. I was totally head-over-heels in love with UMDNJ and got waitlisted. I came to my interview at Western wanting to hate it so that I could go home and focus on getting into UMDNJ, but, I left loving it. You never know what might happen.