A smartphone cannot just be switched to Safe Mode, it requires the phone to actually reboot into Safe Mode. It's not some app or background service that can be enabled/disabled. When your phone is running in its Safe Mode it's actually running the exact same Android operating system but in a different way.
Odds are your credit card wasn't 'hacked' through your phone, you should be focusing your attention to regaining your credit card account via your bank's online web service. The credit card app on your phone is just a user interface that may or may not retain some of your account data, the overwhelming bulk of your account data is stored and managed online, within your bank's servers. That's the data the app references.
Something triggered your phone to reboot itself into its Safe Mode, could be something running on your phone that's the cause or you inadvertently hit the button sequence that restarts your phone into Safe Mode (the process varies depending on just what phone you have).