Creepy Voice chat leakage in game and in client

So once I was playing league with some friends and she closed to her client but she was in my party and i could still hear her even though she wasnt online for awhile. It didn't fix until she relogged and left the party or something. And just now I was playing a game solo when I suddenly heard a voice when I had no programs open. I'm assuming someone else in my team was in voice chat but I swear I heard some kind of brief voice leakage and it surprised me. I'm not sure if there were other cases like these but I think its something worth looking into with the client issue wise.