How can you locate and download a lost app from iCloud?

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All my apps, photos, music, everything from my old phone was downloaded from iCloud onto a new phone except ONE app, my password keeper. The app and all my passwords have been lost. I went to the APP Store to see if I could download it from my "Purchased" list of apps. There is no record of this app ever being purchased from the APP Store so it's like it never existed on my old phone (except that I used it nearly every day). Now I have lost all my passwords. Is there any way to retrieve an app and all the associated data that has seemingly disappeared?