Received my friend's Masteries after I looked at his profile

I was looking at my friend's (Mr PikaChewy) 's mastery named "Run" and I clicked on the mastery page box/icon near the top with a 3 (third mastery page). After that I queued up for a ranked game with a pal of mine, not Mr PikaChewy. After that we got into champ select and I picked my champion and locked in. After that, I realized that my mastery was "Run" even though I don't have a mastery page like that. I tried to change my masteries but was unable to. [Error, relevant error message could not be decided]. That was roughly the error message I got. I tried every single mastery page to try and change it to something I had, but was unable. The way I got it to change was by hitting the little button that lets me edit my mastery pages. Thanks. Very large bug in my opinion.