Possible bug in the library's search function.
That definitely is an odd result. This is a slight bug in our system because it initially not only searches through our system but also Ralston Public Library's and Metropolitan Community College's as well. The titles you mentioned are both Metro books.
However once inside our catalog you are limited to titles that are only available in OPL's system - when you are on this page, for example. If you search through our interface for Metro's catalog, which can be accessed using this link, Mr. Goffman's entries come up again. Our main catalog page explains the different sections for different libraries.
I hope this helps clear things up. Thanks for letting us know about a potential problem.