Started a custom game with no bots. No people either.
Chose to play vel'koz to check it out, but it stopped at the "battle will start soon" thing. Hung for about 5 minutes so i decided to "quit game" which led me to a black screen. So I alt-f4'ed and closed league. Restarted league and it was on screen where it says that i have left a game in progress. Tried to press reconnect, but that doesn't work either.
I used the battlecast vel'koz skin.
You can go in-game now, but the bots are staying in fountain. (like most of these comments are already saying)