Years ago when I was a teenager I had a weekend job working in a clothing chain. Frequently if we were doing a stock take or the manager wanted any store re-arranging to be done, we would be locked in the store after work and the doors would remain locked until we had finished the job, with no one allowed out. This was in the days before mobile phones and obviously we weren't allowed to use the work phones.
I remember on one occasion I worked an extra day during college holidays to help with a stock take, and again we were locked in. My parents were away overnight and I was staying at home with my 15 year old sister, but I didn't actually get home until 2am despite my shift finishing at 9pm as we had all been locked in, and my sister was upset and worried that something had happened to me.
Of course, as a naive teenager I just accepted it but if one of my DCs had a job as a teenager that locked them in I would go absolutely ballistic and would probably cal the police. They wouldn't get away with it nowadays though would they?