You dont get a chest

You need to own the champion in order to receive the chest for that champion. Check out the Hextech Crafting Guide for more information on the requirements for the Hextech components:

https://support.riotgames.com/hc/en-us/articles/207884233-Hextech-Crafting-Guide

Yea its a little wonky

You got it! Unless you own a champion, you can't earn things with a champion that you'll only play for a week. You know, because it's only at most a week. Seven days, as opposed to owning a champion and playing it until the end of time.

Damn it,i didint know it...