Did you get a ban or anything? I doubt it, it sounds like you just got the message asking you not to leave, and were told you weren't eligible for hextech rewards from that particular game.
Which is what LeaverBuster does. It tracks how often stuff like this happens. It also warns you each time it has registered that you did something. This isn't a problem for most players - I've had two leaver penalties in about 2 years of playing:
- A real-life emergency happened during a normal game and I absolutely had to deal with it
- I was playing my first game after a patch update (also a normal) and I was getting insane ping spikes (3000 ping, my normal ping is 26-27 and it stays like that all game), I told my team I was going to restart and be back in 2 minutes, and for some reason League tried to re-download the patch I had just downloaded again! So it took me like 15 minutes to get in at which point my team had just voted to surrender.
Both times I got the message, but I've never received any penalty. Of course not. 2 leaves in 2 years is nothing, it's perfectly acceptable. Shit happens - houses catch on fire, significant others get in car accidents and are at the hospital, power goes out and computers shut down, etc...
The point I'm making here is that while this registered as one leave, you have NOTHING to worry about if you don't leave games willingly and regularly. As long as you play out the huge majority of the games you start, you'll never receive any kind of punishment for leaving.
