Your funds are safe! The wallet in Opera Mini and the standalone MiniPay app are separate. Your funds are still in your Opera Mini wallet.
To transfer them, follow these steps:
Log in to MiniPay inside Opera Mini.
Sign in to the standalone MiniPay app and connect your phone number.
Go back to Opera Mini. You may see a "phone number disconnected" dialog; tap Ignore.
From within Opera Mini, send your funds to the phone number you connected to the standalone app.