You will get a 1 game penalty (loss of LP and a loss no matter the outcome of the game) anytime you leave a game. Think of it like this - you didn’t even play the game, and because of that it was a remake. Had remake not happened, you would’ve gotten a loss. You were penalized because you didn’t connect to the game.
You do not get a low priority queue from one leave. You either have a history of not connecting to, AFKing from, or leaving games, or you did not get a low priority queue from this game. If you are experiencing crashes, it’s your job to use things like the Hextech Repair Tool to repair, repatch, or reinstall your client to resolve the issues. Riot cannot control your patching process which happens on your computer - if your computer or internet connection caused the client to get corrupted, that’s not Riot’s fault and there’s nothing Riot can do about it - you have to fix it by fixing your local client.