The Game Starts but I'm Stuck at 100% in Load Screen.

So today I was playing a game and I loaded up to 100% on the load screen in about 10 seconds like usual. Everyone got to 100% except the other team's Sivir who was stuck at about 21%. I waited for about 5 minutes but then just gave up and reconnected. When i got back, the game had already been going on for 6 minutes.

I'm not sure if this is a bug (or just my computer) but I don't think it has to do with lag or disconnection. Obviously the game recognized that i was loaded because it started right away. But I can't figure out why Sivir wouldn't load on my screen and why I couldn't join the game even though I fully connected according to my load screen.

It seems the server knew i loaded (and started the game asap) but my client didn't (and kept me in load screen for 5 minutes). I believe this is a bug, but if it's just my crappy computer somehow, sorry for wasting your time.

(P.S. It sucks that I thought I was waiting on Sivir to load, while everyone else was actually waiting on me to leave fountain. I would've just reconnected sooner if i knew i was the problem, but I thought it was Sivir.)