GAMEPLAY - Yorick's pet ghoul MVP

I was playing Yorick in an ARAM and somehow managed to spawn an orange ghoul from Yorick's 'e' permanently. It could be targeted (CC'd etc.) by enemy champions but not killed. Even after death it was still there following me around and occasionally attacking enemy turrets/champions to the point where it took a tower on its own and couldn't be stopped by the enemy. I tried reconnecting but it was still there.

I'm not certain how I managed to spawn this perma-ghoul, it took me a while to notice it. Unsure if this is a one off bug or not but it was very game breaking.