We do not have all of the books in WorldCat -- that is a list of books published, not at UR. If you find a book on WorldCat that we do not own, you can order it via Inter-Library Loan and it will be requested from another library and mailed to UR. You can then pick it up from the Circulation Desk and they are usually able to be checked out for 28 days.
Here is information about ordering via ILL: http://library.richmond.edu/services/interlibrary-loan/index.html