Did they take the bus back as well? For me that would be the hard bit as they would have to know the bus time back and get themselves to the bus stop on time. What if the bus was late or didn't show up at all?
Actually, this ^^ has just reminded me of something.
Where I live in London, the buses are every 10 minutes and run throughout the night. The next bus time is displayed on an electronic board at the bus stops. There's even a phone app that will track the arrival of the next bus.
Last August, I stayed in a rural place halfway between Lowestoft and Great Yarmouth. The buses into town only ran every hour, they were frequently late and there was no way of tracking them.
Perhaps this is why some of our replies are so hugely diverse? Either way, the OP gave nowhere near enough information really.
Even where the OP says, I can see it now, here's 20 quid get out of my sight
That doesn't mean it's what actually happened.
So the moral of this story is (as always!), it really does depend on the child and the area 