I live with my current wife in Mexico City, and my ex-wife lives with her new husband here also. My current wife ran into my ex-wife's current husband in an elevator in Santiago, Chile, 6700 km away. They were on business, not vacation, and work in very dissimilar jobs. Besides the awkwardness, I tried to calculate the chances.
Of course the chances of these two specific humans would meet in this specific place in the world at this specific time and date are astronomically small, but it is irrelevant because it would apply to any meeting of any two persons in the world. But for my spouse to meet her spouse abroad in our lifetimes:
Assuming they would work 25 years after our separation but we would live another 40, that they travel abroad 10 days a year in 2 6.7-day work weeks), to 2 of 20 different destinations. Santiago has 48 business class (4 to 5 star) hotels. I assume they worked at least 8 hours a day (no chance of meeting), and slept another 8 (my ex and I assume that this time is also a "no chance" ;-), and I assume that the rest of the day (8 hours at the most, and I assume they were the same 8 hours of the day) they moved about.