It can be frustrating when a book doesn't seem to be where it's supposed to be! Here are some things you can do:
First, double check the catalog to be sure that the status is "AVAILABLE." If SLU's copy is checked out, you can use the MOBIUS catalog to request an available copy from elsewhere in the statewide library network.
Double check the location. The circulating books on floors 2, 4 & 5 of Pius Library will display "Pius Library" next to their call number. If you see something else, like "Reference," "Reserves," "Spec Coll Rare Books," etc, the book is shelved in a special location.
You are welcome & encouraged to ask any library staff member for help. Sometimes all it takes is a second set of eyes to find a book on the shelf, but we will also be happy to help you track down alternative sources.
Text us: 314-582-0194
Call us: 314-977-3087 
Walk in: Mon-Fri 9 am-5 pm 