A search for SDPL, SDPL TO GO, NEW SDPL TO GO, and San Diego Public Library yields No Result at iTunes Store (App Store) as 3/12/2016 from iPad.
Hello, and thank you for contacting the library. Searches for apps on an iPad will default to iPad only apps, whereas the new SDPL To Go was designed specifically for iPhone. If you switch your search to "iPhone" only, it will show in the search results. The app itself will run on both types of devices.
The following link will also take you directly to the app in the iTunes store: https://itunes.apple.com/us/app/sdpl-to-go/id1025094631?mt=8