20 minute afk ban yet got no warning in the game and didnt afk

I was just in a game where our ori was afk until 10 minutes so the whole team agreed to let the team win and we all ran around. I was constantly moving around the fountain and our base along with our team and I got an afk ban for 20 minutes. It's just ridiculous that you would even suspend someone for 20 minutes in the first place as well as not letting them leave the que or chat, look at store, adjust masteries etc. If anyone could help that'd be great.