The closest I came to that scenario was about 2 years back, a night time job.
I was in Douglas, the job was 10km away in Ringaskiddy coming 15km back to town.
Took the job and rang the customer to confirm, all was good.
App crashed half way to Ringaskiddy.
Thankfully I was able to phone the customer again using last dialled number on my phone.
I located him and explaind the story, thankfully his customer app crashed too, so he believed me.
He paid by card through sumup and when the app unfroze 2 hours later I switched it to cash.