Ringgo tells you if a a session is successfully started with a 'payment successful' screen and before that it prompts you to turn on SMS notification if you haven't - it's well worth the bit extra to confirm and alert when a session is about to expire.
So what happened?
Some adjudicators allow appeals on the nonsense that you can't pay for a free thing, so if you have proof you were there for an hour or less you can try that, plus a record of using the app successfully.
Most London councils are now taking a hardline on mishaps with phone bookings even when there is no disadvantage to them, but they can be reminded of their statutory duty to act fairly.