Everyone has the freedom to pick or ban whoever they choose (including you), even if it's something you or someone else on your team wanted. It isn't reportable because it's allowed.
I also suggest you don't go insulting other players just because you're upset. I understand how frustrating it can be to deal with this (trust me, I don't even have to choose my pick intention for it to happen), but doing this just puts you at risk for punishment, even if it's in pre-game or post-game chat. Riot is able to read both of these chat logs.
When it happens to me, I usually play something fun and unconventional that I otherwise don't get a chance to play. That isn't to say I don't try or I troll. I still do my best to help my team and win the game.