I lost 600,000 Doge to an android wallet provider that one day stopped working. It was Ziftr Wallet. The wallet suddenly stopped updating and no one at the company returned any emails or support requests.
Sadly it doesn't appear that Ziftr used any sort of key storage or wallet file that was compatible with other wallets.According to their helpdesk (http://help.ziftrwallet.com/support/home) you had to make backups of the wallet file... and you needed to do so pretty much after any transaction to ensure you had the private keys needed (http://help.ziftrwallet.com/support/solutions/articles/5000626015-how-to-back-up-ziftrwallet-mobile-for-android) as it would appear that this wallet was not an HD wallet with a seed etc
Quote
In the current version of ziftrWALLET Mobile, this action will not apply to any future transactions. In other words, you may want to make a habit of backing up your ziftrWALLET every few days if you’re using it frequently. Also, sending/receiving coins after the backup could cause the backup to lose some coins due to the normal security functions of the blockchain and the distribution of change to newly generated addresses for storage.
If you still have the wallet app installed and/or the app data... it might be possible to extract the private keys from the wallet file if you know what the wallet password was.
