So you're saying when you are waiting for a lobby to fill you do nothing but stare at the lobby screen? That's some damn dedication right there.
No... I leave the page open and do other things in another tab or play MGE/watch videos/listen to music. I've never had a problem with missing the ready up timer because I use the pre-rup button if I'm AFK and the sound prompt is loud enough to be heard over anything else I do and it's pretty distinctive as well. I think I've had the slot bug out on me once or twice and if that happens then either rejoin the slot, ask politely for someone who replaced you to leave or else tough luck, life's a bitch at which point I go find another lobby. I think all in all though I think I've had to leave maybe 3 lobbies out of the 500 and something I've played because of people refusing to leave after I lost my slot to a bug/BS kicking.
It can take someone 5-10 minutes or more to even realize that they have mysteriously been booted from their slot. I often don't notice it until the ready up because I am either in a game or watching TV and don't check back until the ready up prompt at which point it is usually too late, but sometimes, just sometimes I return just to check the progress of filling and find that my I was somehow removed and it hasn't filled yet so there would still be time to do something about it.
So either you were kicked by the lobby leader or your slot reservation bugged out and you got kicked for some reason. If the lobby leader kicked you then ask him why he did it (or if he even did it) or just rejoin the slot and if you bugged out then that's a BS reason which if you read my original response it says
If a lobby leader (or anyone) literally just lost their slot for some BS reason then they're perfectly in their rights to kick that person
Although again, at least in my experience, this is a pretty rare occurance. I'm not gonna bother replying to you anymore though because almost every post I write you try and criticise as if you have some sort of issue with me so I'm just gonna leave you to it.