Does't Riot warn players before banning them?

I tried the pacifist tryndemere challenge (I know it's a dumb challenge but many youtubers such as dyrus, pants and more have tried it) I failed miserably ended up feeding the ennemy team. Althougt I still kept trying and destroyed 4 turrets. I am not a toxic player and this was my first ever offence on this account. According to some boards I saw RIot was supposed to give me a warning before banning me. Will this affect my account forever? I know Riot is severe toward intentionally feeding and I'm glad they are (especially in ranked). I'm just wondering if there will be long lasting effects or if I need to do something. Thank you