[CLIENT] A bug which makes it look like you have someone else's masteries

Whilst waiting in a ranked que I was browsing some EU pro player's profiles, including fat american (imaqtpie). I was looking through his runes and masteries and clicked on some of his pages to see the exact stats when the 'match found' screen popped up and I joined the que. A few moments later I had chosen my champion (vi) and checked my masteries and runes, this is where i noticed there was something off. My list of masteries said i had mastery page 1 through 12 to choose from (i only have 3 mastery pages). I didnt really pay any attention to runes but I assume the same thing happened over there. So I had mastery pages 1 to 12 to choose from and they looked like qt's pages, however when I chose one it said something about an error message not being available or something. I found out that you could refert the error with clicking the edit pencil and saving your masteries again. After that it was alright, but it was a weird experience.

Sorry I don't have any screenshots right now, maybe I can update later but since this is pretty easy to duplicate I hope you guys can take it from here.

Ps, English is not my first language, soz.