Likelihood of meeting someone you know in a solo queue match.

It's been awhile since this happened (couple months ago) but me and my friend were discussing it. There came a day where I started a game and I ran into a guy on the enemy team named CataclysmicDuck. I hadnt seen that name since 2011 and the person asked me if I "Knew a guy named malcolm" Only the guy I knew 5 years ago would have asked that and long story short, League reunited me with a friend after five years.