Uncontrollable champion

So yesterday I was in a ranked game and the game crashed (As usual) during the loading screen. So then I had to restart the game and connect upon doing so my champion (Master Yi) was heading straight to the enemy Nexus as if I clicked on the map to go there. The white line was even there and I was clicking all around, hitting escape trying to get him to stop moving but he continued on till I died by mid turret. So then I thought, okay it might stop since I died but then again he continued to move forward, so my entire team thought I was trolling. I had to close League completely then rejoin again to get it to stop working. Has anyone else encountered this problem?