There are certain - mostly unwritten - golden rules when we look after other people's children, and equally when we entrust our most precious offspring to others.
You tend to let the guest pick which game they will play, or serve them dinner first. When taking other people's children out, I always personally make sure they are strapped in the back of my car, long after my own similar-aged children had learnt to belt up themselves.
It's just the way things are.
So when a while ago, I got a call from a parent to say their husband - who was supposed to be bringing our son home from a school weekend sporting fixture - was on his way back without Jack, my heart was in my mouth before I'd put the phone down.
The parent in question had called to offer to both take and return Jack to a rugby match his son and Jack had both been asked to play in for their school. It was a generous offer and I jumped at the chance – usually one of us is always on the touchline, but it meant we could do something with our two girls instead and Jack was fine about it.
Having breakfast that Saturday morning, Jack was nervous. At 13 it was the first time he'd been asked to represent the school at rugby and he could barely eat his cereal. Fussing about what he should take I told him he needed nothing. His school insists they travel to and from fixtures in their uniform, even on Saturdays, so I said he needed nothing more than his rugby kit.
"Not even my mobile?" asked my son. "No silly," I remember replying. "You'll be with Paul's dad. He's taking you and bringing you back – you just need yourself."
It proved to be a very big mistake on my part.
The first we knew something was amiss was when I got a call from Paul's mum, at about 11.30am. "Just to let you know," she trilled breezily. "Gareth's on his way back with Paul, but they couldn't see Jack, so he's assumed Jack's got a lift home with someone else. You might like to just check with Jack."
My stomach lurched – and I immediately panicked. If someone else hadn't picked him up, our son was a good 12 miles from home, penniless, minus his telephone and in an area of London he was not remotely familiar with.
"Jack hasn't got his telephone with him, or any money," I spluttered. "Are you sure he wasn't there when Gareth was leaving?" I squeaked.
There was silence at the other end of the telephone from the other mum, as the reality of what her husband had done suddenly became clear. Would he have left the ground without his own son? No. So how on earth could he have left without ours?
Over the next hour and three-quarters (I counted every single second) we went through a rollercoaster of emotions.
Frantic telephone calls to other parents who we knew had gone to the match followed. No one had seen Jack, although in fairness they hadn't been looking out for him.
Images of our son in trouble raced through my mind. Had he perhaps collapsed in the toilets of the changing rooms? Remembering he had felt unwell that morning I wondered if in fact it hadn't been nerves at all and something more serious had afflicted him.
Googling the school where I knew Jack had been playing I managed to get hold of the caretaker and asked him to start checking the grounds, and the changing rooms too. In the meantime, my landline and mobile kept ringing – parents who were on their way back were calling to see if there was any sign of Jack, as was Paul's mum.
The images in my mind became darker. Picturing my son wandering about alone, either in his uniform or caked in mud and still in his rugby kit, I knew he would look out of place. Knife crime stories began to dance in my head.
In desperation my husband decided to set off for the school where Jack had been playing and my darling daughters, who had never seen their mother cry so uncontrollably, clumsily made me their first ever cup of coffee.
"Would you cry this much for me mummy if I was missing?" asked the youngest. I was in a dark place.
A little while after my husband had left, he rang to say the traffic was hellish, and he wasn't getting anywhere. "What you need is a blue light to get you through," I said, and a light bulb lit up in my head.
I've never called 999 before, and I hope I never ever have to do it again.
Did you know when a child is reported missing the operator has a set of standard questions they must ask you? No, neither did I.
"Please answer these questions and don't be alarmed," said the operator. Questions such as "has your child exhibited signs of self-harming? Can they swim? Did they have a row with anyone at home this morning? Do they have any distinguishing features? What were they wearing? Are they small for their age?" followed thick and fast.
As I was answering I began crying again: "All these questions you're asking – you should be sending police out to look for him, not wasting time" I sobbed.
"It's OK, madam, we have police out already," soothed the operator, as my daughter ran to the front door excitedly yelling "mummy, mummy, mummy, there's a police car outside!"
And then, magically, unexpectedly, fantastically, as my daughter made the police officer a cup of tea, there was a ring on the door bell, and all hell broke loose as Jack walked in the door.
"Am I in trouble?," his bottom lip trembled as he looked at the policeman sitting in our kitchen.
"No, no, no my love!" I screeched as I threw myself upon my precious first-born, snivelling and snorting into his head as I enveloped him in a mother's hug.
""R-r-r-r-ing Daddy," I instructed the girls, as we set about finding out what had happened, asking questions long into the afternoon, long after the policeman had left with a cheery pat on the head to our boy and the chilling words: "The first hour is the most crucial time when a child goes missing – take your phone next time Jack."
I haven't spoken to the father who left our son and came home without him. Apparently he swears Jack was nowhere to be seen. Jack swears he was the last one standing in the car park and was swept up in the car of a teacher, one of whom always stays at the end of all fixtures to check for stragglers. He was dropped off back at school and then had to get the bus home. Luckily wearing his school uniform meant he had his oyster card on him.
It's taken me over a year to write this piece – the memory of what might have been still haunts me.
What do you think?
Would you be furious if a fellow parent, entrusted with your child's care, did something like this?
Has something similar ever happened to your child?