Title is more or less the explanation, I was party queued (2 people) and got into a game. It loaded me in as a spectator, didn't connect me and I got a 60 minute leaver penalty. Just mentioning it here!
I had this same issue happen. I was queuing with friends and was going to watch a game while waiting. Sometime while I was connecting to watch a game it also at a similar time started the queued match. My friends were talking about the other people in match waiting lobby and I was only spectating. I attempted to leave spectating in order to join or rejoin the match but it didn't let me. When I left spectating it abandoned the match maybe? and I was given the leaver penalty and forced to wait half an hour before my next game.
Same issue. Kinda funny. I wanted to watch a friend while in queue, loaded into the game first, then it switched me into the spectator mode, I left it, but it was too late - got leaver penalty. Disabling the spectator mode while queuing might be a solution, though occasionally it takes a while to find a game, so I thought I had time.