Hi Kari,
It looks like you have uncovered a mystery. In our system, the book you are looking for is supposed to be on hold for someone else. However, the hold has expired without the book being checked out, and I am unable to find it on the shelf where it belongs. I have filled out a book search request form, so soon someone will conduct a thorough search to try and locate this book. When this has happened, they will email you to let you know.
In the meantime, you could submit an interlibrary loan request for this book. Click on Book under New Request in the left sidebar of the screen. Make sure to put a message in the Notes box of the form saying that our copy is missing.
Please let me know if you have any other questions.
Best,
Christin Chenard