Christmas card coincidence

My 13 year old daughter (Lucy) came home from school with a present given to her by a class friend. It was a home-made box, made out of an old re-cycled Christmas card and it was filled with chocolates. He gave one to everybody in the class (30 children). On taking out the chocolates she burst into tears. Inside the box written on the bottom, were the words 'love from Les and Barry'. Les and Barry are her grandparents (my mum and dad) and my mum had passed away two years ago! I could not understand how she had ended up with an old Christmas card that my parents had sent to someone at least two years ago. I immediately phoned my dad to tell him and as I was talking, turned over the box. On the base I could see the imprint of the name and address that my dad had written on the envelope. I relayed this info to my dad who knew at once who he had sent the card to-Mr and Mrs A Crabtree. Even more bizzarely, Mrs Crabtree had died four years ago and they lived 20 miles away. So how had a boy in my daughter's class got an old Christmas card that was at least four years old and out of 30 children she was the one he gave it to? The story gets more interesting-when Lucy asked the boy where he had got the card from, he explained that when he was in year 5 at primary school (they are now in year 9) he had a supply teacher who came in to his class. She showed them how to make the gift boxes out of recycled cards. He loved the idea so much that she gave him some spare cards to take home for him to make into boxes later. He put the cards in a cupboard and forgot about them until this Christmas when he decided to make the boxes again. Ironically, on further investigation it turns out that the supply teacher was in fact the daughter of Mr and Mrs Crabtree and she had taken their old cards into school to use in a craft lesson. What are the chances of a card, been sent by my parents to Mr and Mrs Crabtree (who lived 20 miles away) at least 4 years ago( because that’s when Mrs Crabtree was still alive), taken into a school for a craft lesson, given to a child who put it in a cupboard for four years, then him making it into a box and then out of a class of 30 children, giving it to my daughter when it was originally sent by her grandparents to some old friends? I would be really interested to know what the chances of that happening are? My daughter is convinced it was her deceased grandmas way of wishing her happy Christmas! Who knows?