Roy, that one is mind boggling.
The closest I've got, I think, is quite a family favourite.
When I was 15 I went on a school trip to Newquay, terribly long bus trip back which resulted in lots of kids being sick and we had to stop at the services on the M27 just outside Portsmouth to eat our lunch.
Walking from the bus to the picnic tables I managed to drop all of my lunch in a huge puddle rendering it inedible. Resigned to not eating for the rest of the day I sat there thoroughly miserable with no money left to buy anything, us having spent it the night before.
Now at this time my father was working in the far east and was due to be away for another 2 months or so. However at the moment I sat down at the picnic tables next to the entrance steps to the services a man happened to amusingly fall over and, being 15, we all laughed heartily.
Or at least I did until I happened to notice it was my father!
Dumbfounded I chased after him and he explained what had happened.
Turns out he had got advised to leave the country he was in due to some unrest and so his company had flown him back home for a few weeks for it all to settle down. His flight had been due to fly into Gatwick so he'd have just taken the train down to our house near Brighton to come home but the aircraft had been diverted due to bad weather at Gatwick and he'd landed at Bristol and taken a hire car back but the M4 being snagged up he cut across country to the M27 and ended up falling over right next to me at the Portsmouth services.
Thankfully it also meant he could buy me lunch but the chances of us two ending up at the same spot through random circumstances must have been incredibly minute.
Still doesn't beat Roy's story though