This sort of thing seems to happen a lot to me but one of the strangest was during a business trip to Hong Kong. I was browsing on Nathan Road for gifts to take home when I stopped to examine a tie on a revolving stand. As I tried to turn the stand I realised that someone was attemting to remove an item from the other side and, leaning around to apologise, came face to face with my next door neighbour!
Neither of us even knew the other was away on business and we stood, amongst the million or so other shoppers on that road, laughing loudly at the sheer fluke of it!