They could have called my partner, although he is also an hour away, or my emergency contact who lives close by, if it was an emergency. Where I live, an hour commute is normal. Obviously in a big emergency, I'd hope an ambulance would be called. There was no reception in the meeting room I was in.
However, equally a parent could have been in an exercise class or even out having lunch with a friend or midshop, forgotten their phone, having a nap, at a baby group where you're often not allowed phones, hanging upside down naked playing a flute with a carrot baton up their nose etc etc.
For a child that has only just turned three, when the preschool were fully aware he was still having an odd accident before he started (this is the third at school in the two months), with a published policy that details how they deal with soiling (which they now say they don't do), NOTHING was said to me about having to be available to change him! If it was, I wouldn't have sent him there as it's an appalling policy. When I found out about this policy AFTER he'd had an accident at school and I was called in, I said I was concerned over what would happen if I wasn't wfh and was in the office (my office is an hour away if trains all work - I was with a client only half an hour away yesterday and was meant to continue working with them in their office after the meeting). I was told that of course in that scenario, they would deal with it. They didn't. They have CHOSEN a policy that I don't know of any other nursery or preschool irl adopting!