Volibear invisible glitch

I'm not sure if im just missing something, but I just played a game against a volibear, kalista, riven, kha zix, and heimerdinger and during a pivotal team fight VOLIBEAR DISSAPEARED for about a second and a half. I was playing cho gath and could not target him to get my nom noms on and it resulted in him tossing our adc out of nowhere. we lost the team fight, and thus lost the game to a inhibitor to baron push. This would have been a totally different game if he hadn't gone invisible. Is this a thing? Why did this happen? Please tell me if there is an item or an ability...