Oops got caught!

I knew this would happen and it did! Well I usually depend upon library books for studying during exams. These books plus notes are my only sources. Our library contains huge number of the prescribed books but a few books have very limited copies. So naturally these are unavailable during exam times. So I usually hide the books in another stack before exams. We have open access to the library so its easy to do the job. Just before my Digital Communications exam I switched the book on Image Processing to another rack. I thought I would go to the library next day and issue the book.
When I went to the library next day, I was strolling here and there in the library and after some time i took my Image Processing book to get it issued. When the librarian saw the book he looked straight at me and asked where did I found the book! Boom I was surprised to hear this, but I knew what was coming. I knew all i had to do is deny...deny..deny....
Lib: Where did you find the book?(stares at me)
Z: Uhh I..I found this in another rack..I I suppose someone had switched the book to another rack(looking damn innocent)
Lib: (gets up) Show me where you found the book.
Z: (follows him) I...I found it in the opamp books rack...I was goin through the opamp books and I suddenly saw this book there....
Lib: (stares at me) How on earth you are the only one who found this book!!
Z: I dunno...as I said I ws going through the opamp books.....
Lib: You are not geting this book....six students had asked about the book and we couldnt find it here. If you want this book go get permission from Senior Lib.

I kept saying I found it accidently. But I knew he didnt believe, although he never told me So I just left the room and got the hell out of there. When I was walking home I thought about this again. I think when many students were asking for the same book, librarian must have gone through the database to see if there's any copy left. He must have definitely found one copy is still inside the lib.
Anyways I knew someday or the other this will happen (I was doing this since 2 years now...but only during exams). BTW I dont feel I was morally wrong doing this, was I??