Reporting a Bug

So my friends and I, a team of 5, played a normal Summoner's Rift game. We joined, chose our team and started playing the game. One of my friends, who was a level 4 Ekko mid vs another Ekko mid who was as well level 4, said " Dude there Ekko instantly leveled up from 4 to six." I thought he was lying because that should be impossible. As the game continued, I was a level 4 Shaco Jung, I was coming to gank top. My other friend killed a minion when I was nearby and I suddenly changed from level 4 to level 6 instantly. It happened once in the past 5+ games i've played yesterday. I mean it can be helpful in a way and also can be against you. Hope this get's fixed in future games for me and other Summoner's in the game.