Able to use skins you don't own

While in champ select, if you trade champions with another player who has a skin for that champion, you are able to use that corresponding skin on the traded champ.

For example, what happened to myself.

Summoner 1 picks Lucian to trade with Summoner 2 who picks Gnar

Summoner 2 owns Skin number 2 for Lucian

Summoner 1 does not own any skins for Gnar

When the trade is complete and the game starts, Summoner 1 has skin number 2 for Gnar and Summoner 2 spawns without a skin.

I have yet to replicate this bug but it was very strange to see.