Sounds like the dev or Google pulled it and then removed it from internet connected devices. There's been a crackdown going on at Google over security issues, not saying your app falls into that but if it did... No one ever reads the TOS when they install apps and they can pull it from the play store and they can pull them from your device, Google can pull them from devices if they find serious enough violations. You might be able to find an old mirror on the internet and get the apk to download but once you connect to the internet it might get pulled.