Team Builder Masteries Swap Bug

So my friend decided to try Ahri for the first time, so I was looking at his mastery page to tell him what he should get while we were queing up in team builder. When I closed out his masteries for some reason it switched out my masteries with his. I had to QUICKLY leave the lobby before the game started. I don't know if you still take your friends masteries once you start the game but I didn't want to take the risk. Please look into it. As if team builder didn't have enough wierd stuff going on with it.