Mouse getting stuck in upper right corner at the end of game? {GAMEPLAY}

so i just finished my first game on the new client (we lost, top couldnt change masteries, but thats not a bug, just hard to get to it in time) and in the "defeat" screen, i noticed my mouse kinda dissapeared. i alt-tabbed into another tab, and noticed it would not leave the upper right hand corner, it kept flashing back every time i moved it. i alt-tabbed into task manager, and it was fine, but every other tab the mouse would not move, so i ended the league game and it went right to the client as it normally should. my mouse was no longer stuck. it's only my first game back, but i'll reply to this thread if it happens again.