Masteries of other player in champion select

I played a game, when finished, a guy added me as a friend. I accepted. I went to read his runes, then his masteries. We launched a duo ranked. We chose champs and someone dodged. We waited again and started a new champion select mode. I took another champion (from janna to leona), I wanted to change runes and masteries. Masteries were those of that guy :) (just by name, when i clicked it went back to mine)

Little happy bug... no big deal but funny :)