If I'm understanding what you did right, you didn't have enough sources so you just snagged one from wiki without having any info to attach to it. If that's what you did, then there's no hope for ya and you need to come clean.
However, if there is actually information attached to it (IE you followed a footnote citation on something from the wiki to find the source) you should be able to squeeze by explaining to your teacher that you saw a piece of information that worked for your paper on the wiki page and found that it cited from a reputable academic source.(the book she wants in question) Since the information was there and the source was given to prove it's factual integrity you figured that it was okay to use it, especially since the book was not to be found in your library.
That is actually the most truthful answer you could give your teacher in that situation, as it's not a far stretch of the imagination that's what you would have thought. Despite such a dislike for wikipedia amongst teachers it's actually a great jumping point for research, like most encyclopedias are. I've yet to write a paper where my research doesn't begin with the wiki page for the topic and I've made A's and B's on all of them. I actually just got done writing a paper where the wiki page had most of the books I'd picked out from the library before-hand as sources.
Of course if all you did was slap a source onto your paper that you didn't use that you got from wiki; yeah...you're boned.