Banned for being AFK

[Blurry]

so basically  when i was in my comp game so i chucked on +left +forward because I had to get something from the car and I got kicked I didnt realise it was still on. so when i came back I came on jb started the game i alt tabbed to call my mate on fb 2 mins later I was banned.

I connected to the server at 3:29
I got banned at 09/12/17 03:51 PM 
at 3:22 I ended call and realised I was banned so I messaged forgotten.

I feel like this is an unjustified reason to ban me when was tabbed out side the screen for less then 2 minutes and he straight up banned me I have him on discord and steam and at the least he could of asked if i was there and he gave me no warning not even a kick and I have never done this before so I feel I should of just been kicked or slayed.

EDIT:
HE BANNED ME ON ALL SERVERS