Possible bug?

Basically i've encountered a lot of games this patch and a few others, idk how it happens but its kinda often and its a little hard to explain. Basically we start up the game for a 5v5 summoners rift but we only get 4 people on our team? like idk how it happens but we kinda just have 4 people, like one of ours doesnt even exist, and we go about with our game and clearly we're at a disadvantage but idk one of our players just isnt there. It's really weird and i've lost a lot of games and LP because of it, idk how it happens, but if there is a possible fix, it would be great to see it implemented :)